Entomology

Entomology

Entomology (from Greek ἔντομος, entomos, "that which is cut in pieces or engraved/segmented", hence "insect"; and -λογία, -logia^[1]) is the scientific study of insects, a branch of arthropodology, which in turn is a branch of zoology. In the past the term "insect" was more vague, and historically the definition of entomology included the study of terrestrial animals in other arthropod groups or other phyla, such as arachnids, myriapods, earthworms, land snails, and slugs. This wider meaning may still be encountered in informal use.
Like several of the other fields that are categorized within zoology, entomology is a taxon-based category; any form of scientific study in which there is a focus on insect related inquiries is, by definition, entomology. Entomology therefore includes a cross-section of topics as diverse as molecular genetics, behavior, biomechanics, biochemistry, systematics, physiology, developmental biology, ecology, morphology, paleontology, mathematics, anthropology, robotics, agriculture, nutrition, forensic science, and more.
At some 1.3 million described species, insects account for more than two-thirds of all known organisms, date back some 400 million years, and have many kinds of interactions with humans and other forms of life on earth.
 Branch of zoology dealing with the scientific study of insects, including their taxonomy, morphology, physiology, and ecology. Applied aspects of entomology, such as the harmful and beneficial impact of insects on humans, are also studied.
Insect:

• a small arthropod animal that has six legs and generally one or two pairs of wings:

Insects are usually placed in the class Insecta (see also Hexapoda). The body of a typical adult insect is divided into head, thorax (bearing the legs and wings), and abdomen. The class includes many familiar forms, such as flies, bees, wasps, moths, beetles, grasshoppers, and cockroaches. Insects are the most numerous animals in both numbers of individuals and of different kinds, with more than a million species in all habitats except the sea, and they are of enormous economic importance as pests and carriers of disease, and also as pollinators

Defination of Taxonomy, Systamatics Classification of Insects

Taxonomy: It is derived from Greek word Taxis means arrangement and noms means laws. Taxonomy was first proposed by de Candelie in 1813 for plant classification. It is the theory and principles of classifying organisms. It can also be defined as the branch of Entomology which deals with the study of insect nomenclature and classification the basis of morphological characters.

Systematic: It is developed by early naturalist, Carlous Linnaeus. It is study of diversity and classification of organisms.

Classification: It is the ordering of organisms into a hierarchy of categories.

Class: It is sub group of phylum in which insects of a particular class show similar characters. The class always end with ‘a’ for e.g. Insecta.

Order: It is a group of families showing similar characters. It always ends with ‘ra’ for e.g. Diptera, Coleoptera, and Lepidoptera.

Super Family: It is a group of families showing similar characters. It ends with ‘idea’ for e.g. Papilionoidea.

Family: It is a group of sub families showing characters. It always ends with ‘idea’ for e.g. Noctuidae, Papilionoidae.

Sub Family: It is a group of allied genera showing similar characters. It ends with ‘inae’ for e.g. Papilioniae.

Genera: It is a group of species having similar characters.

Species: It is a group of insects having similar characters which can breed easily. It is last category of classification.

Hierarchy: It is the organization with grades of authority from highest to lowest.

Binomial Nomenclature in Entomology

The insect is evolved to result in a double name, a generic and species name called binomial nomenclature. It was discovered by a Swedish Botanist, Carlous Linnaeus.

The generic and species name should be written in Latin form. If no, it should be underlined separately. The first letter of generic name should be written in capital letters while the first letter of species name should be written in small letters for e.g. Helicoverpa armigera.

Trinomial nomenclature includes generic, species and sub-species e.g. Atherigona varia soccata and Amrasca biguttula.

The Heads of Insects are Oriented in One Three Ways

1. Hypognathous: The long axis of the head is vertical i.e. at right angle to the long axis of the body. The mouthparts point downwards e.g. grasshopper, cockroach etc.

2. Prognathous: The long axis of the head is horizontal and in line with the long axis of the insects body. The mouthparts are directed forwards e.g. Stick insect, soldier caste of termites etc.

3. Opisthognathous: The head is reflexed ventrally so that the mouth parts are directed backwards between the coxae of the front legs e.g. Red cotton bug.

Bases of Insect Classification

1. Presence of Absence of Wings:

a) Apterygota:  e.g. Silverfish.
b) Pterygota: e.g. Butterfly.
Pterygota is divided into:
i. Exopterygota:  e.g. Red Cotton Bug and Cockroach.
ii. Endopterygota: e.g. Moths and Butterflies.

2. Types of Mouth Parts:

a. Chewing and biting: e.g. Cockroach and Grasshopper.
b. Chewing and lapping: e.g. Honeybee.
c. Piercing and sucking: e.g. Red Cotton Bug.
d. Sponging: e.g. Housefly.
e. Siphoning: e.g. Moths Butterflies.
f. Rasping and sucking; e.g. Thrips.

3. Types of Metamorphosis:

a. Ametabolous: e.g. Silverfish.
b. Hemimetabolous: e.g. Cockroach and Grasshopper.
c. Holometabolous: e.g. Moths and Butterflies, Beetle and Weevils.
d. Hypermetabolous: e.g. Blister Beetle.

4. On the Basis of Feeding Habits:

a) Herbivorous: e.g. Stem borer, Aphids and Grasshopper.
b) Carnivorous: e.g. Preying mantid and Lady bird beetle.
c) Omnivorous: e.g. Cockroach.

Herbivorous insects are classified into following groups:
a) Monophagous: e.g. Jowar shoot fly.
b) Oligophagous: e.g. Groundnut leaf miner.
c) Polyphagous: e.g. Helicoverpa armigera.

5. On the basis of reproduction:

a) Viviparous: e.g. Aphid.
b) Oviparous: e.g. Aphid.
c) Parthenogenesis: e.g. Aphid.
d) Polyembryoni: e.g. Larva of Cecidomyiids.
e) Hermaphroditism: e.g. Earthworms.

6. Economic Classification of Insects
           
A) Possessing Economic Importance
B) No Economic Importance (Harmless insects)

I) Harmful

a. Pests of Crops (soil, leaf, tissue fruit borer)
b. Pests of stored products (Rice weevil, Rice moth)
c. Pests of human being & animals (Mosquito, Housefly, Cattle fly, Horsefly, Louse)

II) Beneficial

A) Productive                                          B) Helpful
* Products from secretion of insects     * Aid in pollination – honey bee
* (silk, honey, lac)                                  * Parasitoids (Trichogramma spp.)
* Useful bodies                                  * & Predators (Lady Bird beetle)
i) Cochineal insect – Dye                     * Scientific investigation -Drosophilla spp.
ii) Blister beetle Cantharidin              
iii) Stonefly – fish bait
* Collect plant products (Nectar-Honeybee)  * Destroy Weed – Lantana flies
* Products from plant galls – Tannic acid      * Scavenger – Springtails, Dun
roller

Classification of Insects Based On Morphological Characters

A) Sub Class – Apterygota (Primarily Wingless):

1. Order – Protura                e.g. Proturans
2.  Order – Collembola           e.g. Springtails, Snow fleas
3. Order – Diplura                 e.g. Japyx, diplurans
4. Order – Thysanura  e.g. Silver fish
5. *Order – Microcoryphia     e.g. Bristle tails

B) Sub Class – Pterygota (Winged/Secondarily wingless):

I) Exopterygota:

1. Order – Ephemeroptera                 e.g. Mayflies
2. Order – Odonata                         e.g. Dragonfly, Damselfly
3. Order – Orthoptera                     e.g. Grass hopper, Crickets
4. Order – Dictyotera                      e.g. Cockroach, Mantis
5. Order – Dermaptera                     e.g. Earwig
6. Order – Isoptera                         e.g. Termite
7. Order – Embioptera                     e.g. Web Spinners
8. Order – Plecoptera                     e.g. Stoneflies
9. Order – Zoraptera                      e.g. Zorapternas
10. Order – Psocoptera                  e.g. Psocids, Booklice
11. Order – Mallophaga                  e.g. Chewing lice
12. Order – Anoplura (Siphunculata) e.g. Sucking lice
13. Order – Thysanoptera               e.g. Thrips
14. Order – Hemiptera                    e.g. Bugs
15. Order – Homoptera                   e.g. Aphid, Jassid, Whitefly, Scale, Cicadas, Psyllid

II) Endopterygota:

1. Order – Neuroptera e.g. Ant lion, fish fly, lace wing, snake fly
2. Order – Coleoptera e.g. Beetles, weevils
3. Order – Strepsiptera e.g. Twisted winged insects
4. Order – Mecotera    e.g. Scorpion flies
5. Order – Trichoptera e.g. Caddis flies
6. Order – Lepidoptera e.g. Moths & butterflies
7. Order – Diptera       e.g. Housefly, midge fly, mosquito
8. Order – Siphanoptera e.g. Fleas
9. Order – Hymenoptera e.g. Ant, honey bee, wasp, sawfly

Characteristics of Insect Class Insecta

1. These are tracheated arthropods.
2. It possesses 3 pairs of jointed legs.
3. Body is segmented.
4. Insect body is divided into 3 regions viz., head, thorax and abdomen
5. It possesses a pair of compound eyes & antennae.
6. Two pairs of wings are present in adult stage.

Characteristics of Insect Class Apterygota

1. Wings are primarily absent.
2. Metamorphosis is absent / slight.
3. Adults possess one or more pairs of pregenital appendages.
4. Mandibles are articulated at single point. E.g. Bristle tail, Silverfish, Proturans, Diplurans, Japyx, and Spring tails.

Characteristics of Insect Class Pterygota

1. Adults are winged or secondarily wingless.
2. Metamorphosis is always present.
3. Adults do not moult and do not have pregenital appendages.
4. Mandibles are articulated with head capsule at two points.

Characteristics of Insect Class Exopterygota

1. Wings develop externally.
2. Metamorphosis is incomplete.
3. Immature stages (nymphs) resemble adults in structure, habitat and feeding habits.
4. Pupal stage is absent. E.g. All hemimetabolus insects

Characteristics of Insect Class Endopterygota

1. Wings develop internally.
2. Metamorphosis is complete.
3. Immature stages (larvae) differ from adults in structure, habitat and feeding habits.
4. Pupal stage is present. E.g. All holometabolus insects

Study of Techniques of Collections of, Pinning and Preservation of Insects

Collection of insects will help in obtaining first hand information about the different aspects of inset life such as the host plant, mode of egg laying, feeding, growing and nature of inflicting damage etc. A well identified & classified collection will serve as a valuable reference material of the representative insect fauna of the locality.

Equipments: The following equipments are needed for the purpose of collection, pinning and preservation of insects.

1. Insect collecting net
2. Aspirator
3. Killing bottle
4. Specimen tubes of 10×2.5 cm with cork.
5. Forceps
6. Hand lense of 10× 7.
7. Entomological pins of different sizes
8. Insect storing boxes (45×30×6cm.)
9. Pair of scissors
10. Insect setting boards (35×10cm.)
11. Folding knife
12. Camel hair brush
13. Rearing cages
14. Killing & preserving liquid media.

1. Insect Net: This is prepared by fixing securely a wide ring of 30 cm diameter to a meter long wooden handle. A muslin cloth bag of 60 cm length is fixed to this ring. This net should always be kept dry.

2. Aspirator: This comprises of two holed cork fitted in a specimen tube. Two bend glass tubes are inserted through the holes. One tube of provided with rubber tube to one end & muslin cloth to another end. Aspirator is used to collect the small & delicate insects.

3. Killing Bottle: The collected insects are required to be killed quickly for preservation. For this purpose killing bottles are used. These are the wide mouth jars having thick bottom & tightly fitting corks. It is advisable to have a number of bottles of varying sizes.

Ca, K or sodium cyanide or ethyl acetate or chloroform or 70% alcohol are some of the killing agents used in killing bottles. Potassium cyanide is most toxic killing agent. HCN gas is emitted from the cyanide which kills the insects.

The cyanide killing bottle is made by placing a small quantity of potassium cyanide crystals at the bottom of the bottle wrapped in cotton and over this 1.25 cm dry layer of plaster of Paris is poured. It is allowed to set and dry. Then it is covered by means a disc of blotting paper. This will absorb moisture. The following precautions should be taken in respect of killing bottles.

1. It should be well labeled.
2. Ii should be kept tightly closed.
3. Broken cyanide bottle should be disposed off by burning it into the soil.
4. The separate bottle should be used for killing Lepidopterous and hard bodied insects like beetles and grasshoppers.
5. Over-loading of the bottles should be avoided.
The soft bodied insects like aphids, jassids, thrips or larvae are required to be preserved in fluids. The best killing and preserving agent is 70% alcohol. Before preserving larvae in this medium they should be killed in boiling water.

Mounting the Specimen:

A. Relaxing: The collected and killed insect specimens should be immediately mounted otherwise it becomes brittle & breaks in the process. Hence it should be relaxed in relaxation chamber made out of a wide mouthed airtight jar filled with moistened sand adding few drops of carbolic acid to prevent mould formation. The insects are placed in it for a day for proper relaxation.

B. Pinning: The pinning is the best method for preserving hard bodied insects. The pinning facilitates convenient handling of the specimens for study as well as helps for safe and secure storing. The special rust proof steel pins are used for this purpose, which are generally longer and thinner. As a rule the pins are inserted vertically through the line. The bugs are pinned through the scutellum, grasshoppers through pronotum and beetles through the right elytron. It is desirable to keep 3/4th portion of the pin below and 1/4th portion above the insect body.

C. Setting: The pinned specimens are carefully set on insect setting boards and kept for drying in drying chamber for few days. The wings of the lepidopterous insects and those of Odonata, Neuroptera, Hymenoptera and Diptera etc. are required to be spread after pinning. The general rule in this process is to keep the hind margin of fore wings at right angles to the body and push hind wings underneath these fore wings keeping no gap in between.

D. Labeling: The value of specimen depends upon labeling. The label must contain date and locality of collection, scientific name, host plant and collector’s name.

E. Insect Boxes: The pinned insects must be stored in insect boxes for preserving them safely for a longer period. These boxes are made out of seasonal teak wood in such a way that their joints are insect proof and dust proof. The bottom is covered with cork sheet and prepared for easy pinning. The periodical fumigation of these boxes with EDCT, petrol or naphthalene balls is essential to protect the collection from the attack of the museum pests. On drying insect become very brittle. Extreme care is therefore, be exercised in handling these specimens while storing since specimens with broken legs, antennae or wings are of little value. The best time for collecting insects Is the early hours of morning when the insects are not active. Collection immature stage from the host plants and rearing them to obtain adult forms ensures collection of better specimens.

At night many insects are also attracted to the light. Blue light is more attractive than any other.

Plant Protection Equipment: Dusters

The desired effects of a pesticide can be obtained only if it is applied in an appropriate time and in a proper method. The important methods of applying pesticides are dusting and spraying. The appliances that are used for applying dust and spray formulation of pesticides are called dusters and sprayers, respectively.

Dusters:

All dusters consist essentially of a hopper which usually contains an agitator, an adjustable orifice and delivery tubes. A rotary fan or a bellows provides the conveying air.

A) Manually Operated Dusters:

1. Plunger Duster: It is simple in construction and consists of a dust chamber, a cylinder with a piston or plunger, a rod and a handle. It is useful for small scale use in kitchen garden and in household.

2. Bellows Duster: It has a pair of bellows made of leather, rubber or plastic. The bellows can be worked with a handle just like a Blacksmith does. The dust is placed either in the bellows or in a separate container made of wood, metal or plastic attached to one end of the bellows. The air current that is created runs through the container and drives the dust out through an opening.

3. Hand Rotary Duster: They are also called crank dusters and fan type dusters. They may be shoulder mounted, back or belly mounted. Basically a rotary duster consists of a blower complete with gear box and a hopper with a capacity of about 4-5 kg of dust. The duster is operated by rotating a crank and the motion is transmitted through the gear to the blower. The air current produced by the blower draws the dust from the hopper and discharges out through the delivery tube which may have one or two nozzles. It is used for dusting field crops, vegetables and small trees and bushes in orchards. The efficiency of these dusters is 1 to 1.5 ha/day.

B) Power Operated Duster:

1) Engine operated dusters
2) Wet dusters

Plant Protection Equipment Sprayers

Depending upon the quantity of spray fluid required per unit area, the sprays are described as i) High volume sprays ii) Low volume sprays and iii) Ultra – low volume sprays. The spray fluid of 450 to 1000 liters; 12 to 125 liters and 0.5 to 6 liters will be required to cover one hectare of field crop with above mentioned sprays respectively. However the droplet size of these three sprays varies from 250 to 500, 150 to 250 and 70 to 150 microns respectively.

Types of Sprayers:

I) High Volume Sprayers:

A) Manually Operated Hydraulic Sprayers:

1. Hand Syringe:

It consists of a cylinder and a plunger, spray fluid has to be contained in a separate tank. The liquid is drawn on return stroke of the plunger and ejected during the compression stroke. After each ejected the spray fluid has to be drawn in. It is useful for small scale spraying in kitchen gardens and pot plants.

2. Bucker Sprayer or Stirrup Pump:

It may consist either of a double acting pump with two cylinders or a single acting pump with one cylinder. The other parts of the sprayer are the plunger assembly, foot value assembly, hose, lance and nozzle, a stirrup and an adjustable foot rest. The pump has to be put in a  bucket of any container having the spray fluid. In the single acting pump the spray discharge is discontinuous since the fluid is ejected only during the downward compression stroke, while in the double acting pump the discharge is continuous as the fluid is discharged during both sucdon and pressures strokes. This type of sprayer is useful for spraying small trees. Area covered per day is 0.5 to 0.8 ha.

3. Knapsack Sprayer:

This type of sprayer has a flat or bean shaped tank. The tank has a capacity of 10 to 30 liters and is made of galvanized iron, brass stainless steel or plastic. It is similar to bucket type in principle. It is operated by a lever handle provided inside the tank and it moves up and down inside the container due to the movements of the pump lever. It is user for spraying field crops vegetables and nurseries. The area covered per day is 0.8 to 1 ha.

4. Rocker Sprayer or Gatoor Pump:

It consists of a pump assembly, a rocking lever, pressure chamber, and suction hose with a strainer, delivery hose, cut-off valve and spray lance with nozzle. By rocking movement of the lever pressure can be built in the pressure chamber and this helps to force the liquid through the nozzle. There is no built in tank. It can be used for spraying trees and tall field crops. It covers about 1.5 to 2 hectares of area in a day.

5. Foot Sprayer or Pedal Pump:

A pedal pump consists of a vertical pressure chamber mounted on to a stand and a plunger assembly with the plunger rod attacked to a pedal in addition to a suction hose with a strainer, a delivery hose with an extension rod and spray nozzle. It has no built in tank. It works on the same principle as the rocker sprayer except that the pedal is worked up and down by foot in this case where the rocker in a rocker sprayer is operated forward and backward by hand. In both cases continuous operation of pedal or rocker is required to maintain high pressure for uniform spraying. It is used for spraying agricultural crops as well as small fruit trees. About 1 to 1.5 ha area can be sprayed in a day.

B) Manually Operated Pneumatic Sprayers:

In the sprayer working with air compression system, the pressure is developed on the air contained in the spray tank, hence some air should be allowed to remained in the tank which therefore, should not be filled with spray fluid completely. They do not have agitators and hence are not useful spraying materials which settle down quickly.

1. Hand Sprayer or Ganesh Pump or Atomizer:

The container for the spray fluid also acts as the pressure chamber. An air pump attacked to the chamber projects inside. The inner end of the discharge pipe runs down to the bottom of the container and its outlet terminates in a nozzle. The tank is filled about 3/4th of it and the pump is worked force air into the space to build sufficient pressure upon the spray fluid. These sprayers are used extensively in kitchen gardens, in glasshouses and in doors against house-hold insects. The capacity of tank is up to one liter, if used in field it can cover an area of 0.1 ha in a day.

2. Knapsack Sprayer:

They are adopted for spraying large quantities of liquids. It comprises a tank for holding the spray as well as compressed air, a vertical air pump with a handle, filling hole with a strainer, spray lance with nozzle and release and shut-off devices. The tank is provided a convenient rest with the back of the operator and has shoulder straps that allow it to be carried by him. These sprayers are used against agricultural pests and mosquito control operations. The capacity of tank is 12 to 16 liters. This pump covers an area of about 0.8 to 1.2 ha in a day.

C) Power Operated Hydraulic Sprayer:

A power operated hydraulic sprayer generally consists of a petrol engine and a framework. The following are some of the power operated hydraulic sprayer.

1. Stretcher sprayer
2. Wheel-barrow sprayer
3. Traction sprayer
4. Power take off sprayer

D) Power Operated Pneumatic Sprayers:

It consists of the following sprayers
1. Portable sprayers
2. Traction sprayers

II) Low Volume Sprayers:

Since in these sprayers the spray fluid is atomized with the help of an air stream at high velocity, they are called mist blowers or power sprayers. The tank in these is made of a thick polyethylene and has a capacity of 10 liters. The fuel tank capacity is 1.0 to 1.5 liters. It is provided with 1.2 to 3.0 hp petrol engine. This can also be used for dusting provided suitable accessories. The area covered by these sprayers is about 2 ha in a day.

III) Ultra Low Volume Sprayers:

The pesticide in ULV formulation is used undiluted at a quantity less than 6 liters/ha and usually at 0.5 to 2.0 liters/ha for field crops. The droplet size varies from 20-150 micron with ground spraying equipment for ULV spray an area of 5 ha can be covered in a day. E.g. Controlled Droplet Applicator (CDA)

Handlings of Pesticides

Pesticides being toxic to human beings and domestic animals should be handled with at most care. The following precautions should always be observed.
The pesticides should always be stored in their original containers and kept in a locked cupboard where they are out of reach of the children and domestic animals.

1. They should be kept or stored away from food or feed stuffs and medicine.
2. The instruction found on the labels should be carefully read and strictly followed.
3.  Bags and containers of pesticides should be cut open with a separate knife intended for such purposes.
4. The empty containers, after the use of the chemical, should be destroyed and should not be put into some other use.
5. While preparing the spray solutions bare hands should not be used for mixing the chemical with water.
6. Inhaling of pesticide sprays or dusts, and smoking, chewing, eating or drinking while mixing or applying the chemicals should be avoided.
7.  Spilling of pesticides on skin or clothing should as far as possible be avoided. The clothes should be washed after each operation.
8. Particles or drops of pesticides, which may accidentally get into eyes should be flushed out immediately with large volumes of clean water.
9. It is preferable that protective clothing’s and devices are used while handling poisonous chemicals to avoid exposure to sprays or drifts.
10. Dusting or spraying should never be done against the wind and it is preferable to have them done in cool and calm weather.
11. Sprayer nozzles should not be blown by mouth if gets blocked while spraying. Washers and other contaminated parts should be buried.
12 After handling pesticides hands, face and body should be washed and clothing changed.
13. Washing of equipment after use and containers in or hear wells, or streams should be avoided.
14. Person engaged in handling pesticides should undergo regular medical checkup.
15. In case of any suspected poisoning due to insecticides the nearest physician should be called immediately.

Introduction to Crop Pest

Pest:

Any living organism that causes harm to man, his crops or animals or possession or simply cause annoyance to human being, qualifies to refer as pest

Pest Management:

It is the system in the context of associated environment & population dynamics of the pest, utilizes all possible techniques or practices to maintain the pest population that will not cause economic damage or losses. Pests will be dealt in respect with the following points.

Nomenclature: (Taxonomic Position):

Every living organisms are known by common name and scientific name. Particular insects are known by common name in certain area / locality & not all over the world. They are recognized in scientific community by scientific names which consist of two names, viz. Earias vitella the first name indicates genera & the second specify the species mime. This system of no­menclature is called as binomial system of nomenclature. Similarly, trinomial system of naming is in existence for some insects where in three names are given e.g.

Pyrilla perpusilla coimbatorensis
Pyrilla perpusilla pusana

Marks of Identification:

Description of different developmental stages for e.g. shoot fly egg, larva, pupa & adult is important for correct identification of pest.

Hosts:

These are the plants on which insect use lo feed upon for completion of its life cycle. When main host is not available insect can feed on other hosts for survival is called alternate hosts.

Life history:

Means the development of insect for instance in most of the insects development take place from egg to adult stages, e.g. Jowar shoot fly. The object to study the life history is to find out certain weak points of the insects viz. site of pupalation, carry over from one season to next, habit & habitat of pest. These are to be pointed out for deciding the control strategies of the pests.

Nature of damage:

There is hardly any plant which is not infested by the pest. Pests injure to host plants. They damage one or the other parts of the plant viz. roots (root feeders), Stem / shoot (stem borers) leaves (leaf feeders), buds, flowers, fruits (fruit borers) & grains also. Depending upon feeding habit, pests are categorized as sucking pests & chewing pests. Accordingly the symptoms are produced on damaged plant parts.

Management of the Pest:

While managing the pest there should be an integrated pest management (IPM) approach in order to keep pest population below a level of economically acceptable damage (ETL)

 Jowar Shoot Fly & Jowar Stem Borer - Pests of Jowar

A. Jowar Shoot Fly

Scientific Name:  Atherigona soccata Rond.
Class & Order: Anthomyidae – Diptera

Economic Importance: It is one of the serious pests of sorghum in India. The Pest attacks the crop only in early stage of growth and infestation goes up to 80%. The high yielding hybrids are more susceptible to the attack of this fly. The total loss in yield is sometimes as high as 60%. The pest is very serious on kharif and Rabi crops in Maharashtra State.

Marks of Identification: Adult fly is dark grey, like the common house fly but much smaller in size, 6 & 4 dark spots on abdominal segments of female & male respectively (arranged in rows of two) Maggot are legless, tapering towards head, pale yellow, small ( 10- 12 mm in length ).

Host plants: Jowar and grasses like Andropogan sorghum, Cynodon dactylon and Panicum spp.

Life history: Eggs: Eggs are average 40 eggs are laid by a female singly on lower surface of leaves & tender stem. Incubation period is of 2-3 days. Larva: larval period 10 to 12 days. Four larval instars are present. Pupa: Pupation in stem. Pupal period is about a week. Adult longevity is 12-1 4 days. Life cycle completes in 2-3 weeks. Several generations in a year. Carry over -The pest over winters in adult stage on grasses.

Seasonal occurrence: The insect attacks the seedlings and late sown crops are attacked badly. The attack is severe during July to October. Cloudy weather favours multiplication of the insect. In rabi, early sown crop suffers more and hence sowing should be delayed possibly

Nature of Damage: Maggots on hatching from the eggs bore into the central shoots of seedlings and kill the growing point, producing "dead hearts". They feed on the decaying core of the shoots. Subsequently on death of central shoot, plant gives out tillers and plant gets bushy appearance.

Management Practices:

1. Sow the crop as early as possible i.e. immediately after the onset of rains or within 15 days after receiving of rains. Increase the seed rate to make up the loss.
2. Use the seeds treated with carbofuran 50 SP @ 5% a.i. by wt. of seed (Gum Arabic as sticker) or carbosulfan 25 STD @ 200 gm / kg of seed OR 3% carbofuran granuals @ 5 kgs /50 kgs of seed by using slurry of wheat flour as sticker. OR Application of phorate 10 gm @ 10 Kg / ha in soil at sowing OR Spray the crop with 0.05% endosulfan soon as 10% seedlings are infested or 1 egg / 10seedlings are noticed.
3. Removal and destruction of affected shoots along with the larvae.
4. Use resistant (Maldandi 35-1) or less susceptible varieties like R.S. V.9 R (Swati), S.P. V86 for planting.

B. Jowar Stem Borer

Scientific Name: Chilo partellus S.
Class & Order: Pyralidae – Lepidoptera

Economic Importance: It is one of the major pests of Jowar and has a wide distribution. The infestation is noticed till harvest and the grown up plants when damaged loose their vigour and put forth week ears. The infestation is more pronounced on rabi and hot weather crops.

Marks of Identification: Moths - medium sized, straw coloured, yellowish grey forewings. The hind wings are whitish. Caterpillar - ditty white, brown head, many dark spots on the body, 12- 20 mm in length.

Host plants: Although principle hosts are Jowar and maize, it has also been recorded on Sugarcane, Ragi and certain grasses.

Life history: Eggs - about 300 eggs are laid, on leaves in clusters, incubation period about 6 days larval period:  3-4 weeks. Pupa: pupation in stem. Pupal period 7-10 days. Before pupation larva prepare a hole on stem at ground level for the moth to escape / come out. Adult longevity 2-4 days

Life cycle: completed in 6-7 weeks. About 4-5 generations are completed in a year.

Carry Over: The pest hibernates in the larval stage in stubbles. Seasonal occurrence: The pest is generally active from July to November. The infestation is more on rabi & summer crops.

Nature of damage: On hatching from the eggs, the larvae initially feed on tender leaf whorls causing series of holes in the leaf lamina and later bore into the stems, feed on the central shoots causing their death, commonly known as “dead hearts”
 
Management Practices: Preventive and curative measures.

Preventive:

1. Collection and destruction of stubbles after the harvest of crop to kill hibernating larvae
2. Increase the seed rate to compensate the loss.
3. Follow proper crop rotation (with non host crop).
4. Use of light traps.

Curative:

1. Removal & destruction of affected shoots along with the larvae.
2. Spraying with 0.05% endosulfan or 0.2%carbaryl OR whorl application of endosulfan 4G @ 10kg/ha, when 10% plants are infested.

Aphids & Delphacids - Pests of Jowar

A. Aphids:

Scientific Name: i) Rhophalosiphum maidis F. ii) Aphis sacchari Z
Class & Order: Aphididae: Hemiptera

B. Delphacids:

Scientific Name: Peregrinus maidis A.
Class & Order: Delphacidae: Hemiptera.

Economic Importance: They are the most important pests of Jowar. The infestation is usually high on rabi crop. The yield is adversely affected and the fodder quality also deteriorates.

Marks of Identification: Aphids-Adults are minute, soft bodied, oblong, light green or pale yellow Cornicles: They are characterized by the presence of 2 tubes like structures on the dorsal side of abdomen. They are generally wingless but winged forms are often noticed usually in the beginning and towards end of season for migration to other crops.

Nymphs: Smaller and greenish. Aphids are found in large numbers on lower surface of leaves and leaf whorls and do not move unless disturbed.

Delphacids: Adults: Wedge, pale yellow, walk diagonally. Nymphs -like adults but wingless. Delphacids found mostly in the whorl of the plant.

Host plants: Jowar, bajara, other cereals and sugarcane.

Life history: Aphids - only females are noticed in Maharashtra. Reproduction parthenogetically on an average each female produce about 42 young ones within period of 5 days. Nymphs moults 4 times in a period of 5 days. A generation is completed in about 2 weeks.

Delphacids: Eggs - about 150 eggs are laid in tissues incubation period 7-8days nymphal period 15-19 days (moults 5 times) Life cycle completed in about a month time.

Nature of damage: Both nymphs and adults suck the sap from plant especially from the leaves. As a result the leaves turn yellow and in case of heavy infestation the plants remain stunted. Their injury causes oozing of sap which crystallizes on evaporation forming sugary material called "Chikta" OR ""Sugary Disease". Due to sugary material oozing out of the plant and honey due excreted by the insects, the sooty mould develops and the leaves turn blackish. The yield is adversely affected and the fodder quality also deteriorates.

Management Practices: Spraying with dimethoate / quinalphos at 0.03% or formothion / monocrotophos /methyl demeton at 0.02%OR dusting the crop with endosulfan 4D / quindphos 1.5 D @20kg'lia. Spraying is more effective than dusting.

Definition of Biological Control

Biological control, when considered from the ecological view point as a phase of natural control, can be defined as “The action of parasites, predators or pathogens in maintaining another organism’s population density at a lower average than would occur in their absence”. (Paul DeBach, 1964).

This definition is more demographic and ecological in context, but it does not explain the mechanism of control or regulation. It is a factual type of definition in that Biological control can be measured experimentally but man’s activity or manipulation of natural enemies not implicit / exhibited. Hence, in more precise way as an applied control, Biological control can be defined as “The destruction or suppression of undesirable insects, other animals or plants by the introduction, encouragement or artificial increase of their natural enemies”.

Types of Biological Control

Biological control involves regulation of organism’s population density at any given level by natural enemies. If Biological control factors are responsible for population regulation of an organism below density which would be adverse to man’s interest, then it is a case of successful biological control in economic sense.

1. Partial Biological Control:

If control is achieved at somewhat higher average population densities than it is economically satisfactory, this is sometimes alluded to as partial Biological control.

2. Substantial Biological Control:

If Biological control can be substantially successful economically for a period of time, the only partially so far a subsequent period. Here a degree of Biological control is evaluated on economic yard stick.

3. Complete Biological Control:

If Biological agent is successful economically for a very long period of time. So far as such success has not yet been achieved. For example, Rodolia cardinalis on cottony cushion scale in citrus Epiricania melanoleuca on pyrilla in sugarcane. Outstanding economic feature of successful biological control is that once achieved, it is essentially permanent. Also, it does agree with man’s purposeful activity.

Field of Biological Control

Study includes basic as well as applied aspects viz. introduction, conservation, augmentation of natural enemies for the regulation of pest population density.

Basic Studies:

It includes research on fundamental aspects like taxonomy, biology, physiology, genetics, Ecology and demography, behavior, culturing methods and nutrition.

Applied Studies:

Introduction of Natural Enemies:

Purposeful introduction of new natural enemies is usually based on the fact that many, if not most, agricultural pests have been accidentally introduced into the area concerned where there indigenous natural enemies have been designed. For example: Potato tuber moth is a native of South America but introduced in India via Italy along with seed potato.

Conservation of Natural Enemies:

Another approach to the enhancement of biological control would be to modify the environment in such a way that any adverse environment effect would be eliminated.

Augmentation:

This phase of biological control deals with manipulation of natural enemies themselves in order to make them more efficient in the regulation of host population density.

Pest residue:

So as to conserve natural enemies there must be pest population at certain level.

Scope of Biological Control

In the years ahead, workers in Biological control of insects, mites and seed pest suppression must continue to deepen and broaden their efforts, as this field has received great enthusiastic acclaim during past century. These research workers showed successful practical results in more than 60 countries of the world. The partially exploited field has several dimension of future scope.

1. Promoting Basic Research:

There is lot of scope to intensify the studies which can improve and synergize the biological control. Basic research areas in the field of biology, ecology, biosystematics, behavior, biochemistry, population dynamics etc. have great contributing value to biological suppression which needs to be studied. This studio would help grenuy in the application of IPM strategies of the pest.

2. Scope to Exploit the Bioagent on Crop Pest:

About 98 % of the insects pests are regulated naturally through natural enemies. However, it is reported that only 5% of the world insect pest species have ever been the subject of entomophage introduction (DeBack, 1974). It is estimated that 70% of parasitic hymenoptera are still undescribed species.

3. Help to Reduce Pollution Hazards:

Utilization of bioagent can help in establishment of population regulation process of serious pests by reducing the load of toxic insecticides and their side effects.

4. Necessity to Intensify of New Horizons of Biological Control:

Importation and use of parasitoids and predators is popular concept of biological control, which gave good success in several cases. Similarly new trends such as use of biotypes, strains, hybrids of parasites, use of novel biopesticides like entomogenous fungi, viruses are to be search properly and its harmonious use in pest suppression needs to be exploited.

5. Adoption of Biological Control Methods in Agro Industries:

Although use of bioagent has many benefits but there is need to adjust with other methods like chemical control of pest. The pesticides should be less toxic to natural enemies and needs to be identified and employed in pest control suppression. For example, Endosulfan safe to many predators and social insects.
Biological control helps in maintaining ‘Balance of Nature’ as it is the phase of natural control.

Practical significance of Biocontrol (Advantages)

1. It is exercised in a wide area.

2. The application of biotic agent is easy and possible in inaccessible areas like dense forest.

3. It is safe for humans and animal health.

4. The biotic agents survive in nature till the pest is prevalent.

5. It is a cheaper method if successfully deployed and persuaded.

6. It is a self perpetuating in nature.

7. It has no risk of environment pollution.

8. It does not require and special equipment to apply and can be mass multiplied at farmer’s level.

9. It may provide/generate employment revenues to rural people.

10. No problem of pest resistance and resurgence.

Constrains in the adoption of Biocontrol (Limitations)

Biocontrol is slow process and takes little more time to achieve control of crop pests. The possible constrains are:

A) At farmer’s Level:

1. Non availability of biotic agents for field application timely.
2. Illiteracy among farmer as they have no access to new technologies to read.
3. Small holdings may cause migration of bioagent.
4. Inclination towards use of chemical pesticides.
5. Non availability of popular literature.
6. Population lacking.

B) At Government Level:

1 Relatively less attention to Biocontrol projects than chemical industries.
2. Importation of biotic agents.
3. Mass production of biotic agents limited techniques for indigenous and exotic use.
4. Field Utilization of biotic agents.
5. Integration of bioagent with pesticides.
6. Laboratory evaluation of biotic agents and their field efficiency.
7. Transfer of technology requires more attention.

Important Terms used in Biological Control of Crop Pests - I

Accretive Release:

A method of periodic introduction of biotic agents in which annual early season liberations against fairly abundant pest populations allow the beneficial organism population to increase naturally in response to rising pest densities as the season progresses.

Agroccosystem:

The modified and simplified system of plants, animals and habitat used for human agricultural purposes.

Antibiosis:

According to Painter (1951), it refers preventative, injurious or destructive effects on the insect life history which result from the insect’s use of a resistant host variety or species for food.

Antifeedant:

A natural synthetic chemical substance which acts either to inhibit the stimulation of gustatory receptors which normally recognize suitable food, or to stimulate receptors which elicit a negative response to deterrent chemicals.

Arrhenotoky:

A facultative type of parthogenetic reproductive in which only male progeny are produced.

Augmentation:

It is the process which involves to improve the effectiveness of natural enemies  by manipulating either mass production, periodic colonization or by genetic improvement.

Autodial Control:

The use of an insect species against itself, usually through, some means of genetic modification, to suppress or eradicate its natural population.

Autoparasitism:

A special type of hyper parasitism in which the female develops as primary parasitoid, but the male is a secondary parasitoid through females of its own species.

Important Terms used in Biological Control of Crop Pests – II

Balance of Nature:

The natural tendency of plant and animal populations, resulting from natural regulative processes in an undisturbed environment, to neither decline in numbers to extinction, nor increase to infinite density.

Biological Control:

Biological pest suppression in its narrow, classical sense, usually restricted to the introduction by man, of parasitoids, predators, and/or pathogenic micro organisms to suppress population of plant or animal pests.

Biological Insect Pest Suppression:

The use or encouragement by man, of living organism or their products for the population reduction of pest insects.

Biotype:

A biological strain of an organism, morphologically indistinguishable from other member of its species, but exhibiting distinctive physiological characteristics; particularly  in regard to its ability to successfully utilize pest-resistant host organisms or to act as an effective beneficial species.

Cleptoparasitism:

A type of parasitism in which the adult parasitoid preferentially appropriates for its own progeny the previously paralyzed and parasitized host of another parasitoid.

Colonization:

The controlled release of a quality of biological control agents in a favorable environment for the purpose of permanent or temporary establishment.

Conservation:

It is the process involved in manipulation of environment to favour natural enemies either by removing or modifying the adverse effects or by providing the lacking pre-requisities.

Density dependent factor:

Refers to mortality factors or processes in the environment which destroys an increasing percentage of the subject population as the numerical population density increase and vice versa.

Density Independent Factor:

Refers to mortality factors or processes in the environment which destroys a relatively constant percentage of the subject population regardless of changes in its density.

Denterotoky:

A type of parthenogenetic reproduction in which the progeny of unmated females may consist of both males and females.

Important Terms used in Biological Control of Crop Pests – III

Ecological Niche:

The place an organism occupies in its biotic relationships and physical environment as determined by its particular structural adaptations, physiological adjustments, and developed behavioral patterns.

Economic Threshold:

A population density concept which allows the determination of the point at which pest numbers are sufficient to cause economic injury unless suppressive action is taken.

Ectoparasitoid:

An insect parasite which develops externally on its arthropod host.

Endoparasitoid:

An insect parasite which develops within the arthropods host.

Endotoxin:

An toxin substance formed by certain bacteria and retained within their vegetative cells (e.g. in Bacillus thuringiensis, the endotoxin occurs as  a part of the crystal shaped parasporal body).

Entomogenous:

Refers to organisms (usually micro organisms) growing in or on the bodies of insects.

Entomopathogenic:

Capable of causing disease in insects.

Entomophagous:

Refers to the consumption of insects or their parts, insectivorous.

Entomophilic:

Insect-loving.

Enzootic:

Refers to a disease condition (or sometimes a pest) which is constantly present in an area, but at a low rate of incidence.

Epizootic:

An outbreak of a disease (or sometime a pest) in which is an unusually high number of cases (or density of the pest).

Exotic:

A soluble toxic substance produced by certain bacteria and found in their surrounding growth medium.

Factitious Host:

An unnatural but acceptable host used in laboratory propagation of beneficial organisms.

Facultative Parasitism:

Here in reference to nematodes which may either parasitize healthy insect, or develop in some other way in the environment (e.g. mycetophagy) if no insect host is encountered.

Facultative Pathogen:

A micro organism which is capable of growth and reproduction in either a non living medium or living host; in the latter instance, a disease condition of the host may arise.

Fortuitous Biological Insect Pest Suppression:

The desirable but accidental movement of exotic beneficial organisms to new areas and/or new pests, where pest population suppression eventually results; or the successful population regulation of exotic pests by indigenous natural enemies.

Important Terms used in Biological Control of Crop Pests – IV

Granulosis:

An insect viral disease characterized by the presence of minute granular inclusions (capsules) in the infected cells.

Gregarious Parasitoid:

An insect parasite which normally develops successfully at a rate of two or more individuals per arthropod host.

Heteroxenous:

Describes a species which require the use of more than one host species to successfully complete its annual life cycle.

Inclusion Body:

The proteinaceous or crystal like structure produced in insect cells infected with certain viral pathogens. (It occurs in various shapes and sizes and usually encloses a number of replicated virons).

Indigenous:

Native to a particular region or country.

Inundative Release:

A method of periodic introduction of biotic agents which is analogous to insecticide treatment in that a greater amount of the liberated material is used than is actually effective repetition m may be necessary and the effect is more less immediate.

International Unit (IU):

An arbitrarily set basis for comparing the efficacy of insect pathogenic Bacillus thuringiensis preparations. It is one thousand of the amounts of insecticidal activity contained in one million of a preparation of the primary standard E-61 strain B-t., as measured by bioassay against certain caterpillars e.g. A standard B-t. strain (HD-1-S-1971) has assigned a potency of 18000 IU/mg against the cabbage looper.

IOBC:

(International Organization for Biological Control of noxious animals and plants an affiliate for the International Union of Biological Sciences): A global organization of government units and individual interested in biological pest suppression headquartered in Zurich, Switzerland. Major objective include disseinination of information, coordination and promotion of research and application of biological pest suppression. Publisher of the journal, Entomophaga.

Important Terms used in Biological Control of Crop Pests – V

Life Table:

A device for expressing in an orderly fashion, observations on the changing density of an insect population in time and space and the processes which direct those changes, especially in relation to the age-specific distribution of mortality and its causes.

Microbial Insecticide:

A pathogenic microorganism or its products (e.g. toxins) when used by man to suppress an insect population.

Microbial Pathogen:

A microorganism which causes disease in its host; more specifically, a term used in preference to microbial “insecticide” to denote a microorganism used by man to suppress insect pest population.

Monoculture:

The cultivation of a single crop species over large areas without provision for diversity or use of the land in any other way.

Monophagous:

The term restricted to the use of only one plant or animal species as host or prey.

Monoxenous:

Describes a species which requires only a single host species on which it successfully complete its annual life cycle.

Multiparasitism:

A condition resulting from the simultaneous use of a single host individual by two or more species of primary parasitoids.

Multivoltine:

Having two or more complete generations annually.

Natural Control:

The process of dynamic equilibrium which maintains the characteristic mean density of a wild population within particular upper and lower limits, over a period of time, by a complex combination of all the additive conditioning, and subtractive processes striking that wild population.

Natural Enemies:

Strictly, the parasitoids, predators, and pathogenic microorganisms associated naturally with a specific wild population of plants or animals, and causing mortality or debility to the individual thereof; often used in a general sense for all parasitoids, predators, and pathogens.

Obligate Parasitism:

Here in reference to nematodes which must develop parasitically and cannot reproduce and complete growth away from.

Obligate Pathogen:

A disease causing microorganism which requires a living host to grow and reproduce.

Important Terms used in Biological Control of Crop Pests – VI

1. Parasite:

An animal species which level on or in a larger animal, the host, feeding upon it, and frequently destroying it. A parasite needs only one or part of one host to reach maturity.

2. Parasitism:

A qualitative term referring to a kind of symbiosis in which one party (the parasite) lives at the expense of the other (the host), contributing nothing to the relationships and frequently destroying the host in the process.

3. Parasitization:

A quantitative term referring to the proportion of a host population attacked by parasites.

4. Parasitoid:

An insect parasite of an arthropod parasitic only in its immature stages, destroying its host in the process of development and free living as an adult.

5. Periodic release:

A method of beneficial organism introduction which involves repeated liberations to artificially maintain high population levels of indigenous biotic agents in situations which such levels are unattainable naturally.

6. Polyhedrosis:

An insect viral disease characterized by formation of polyhedron shaped inclusions in the infected calls. The disease is known as a nuclear Polyhedrosis or nucleopolyhedrosis.

7. Polyphagous:

Adapted to the use of wide variety of plant or animal species as hosts or prey.

8. Population Dynamics:

The study of numerical changes in populations of living organisms in time and space and of the processes which cause such variations.

9. Predator:

An animal which feeds upon other animals (prey) that are usually smaller and weaker than itself, frequently devouring them completely and rapidly. A predator most often is required to seek out and attack more than one prey to reach maturity.

10. Primary Parasitoid:

An insect parasite of any arthropod which is not itself parasitic.

11. Protelean Parasite:

An insect species in which only the immature stages are parasitic.

12. Secondary Parasitoid:

An insect species of a primary parasitoid.

13. Septicemia:

A morbid condition caused by invasion and multiplication of microorganisms in the blood.

14. Solitary Parasitism:

All insect parasite which normally develops at a rate of one individual per arthropod host.

15. Superparasitism:

A condition resulting from the use of a single host individual by more individual parasitoids of the same species than it can successfully sustain to maturity because of nutritional limitations.

16. Symbiosis:

The living together in close association of two or more species of organisms.

17. Thelyotoky:

A type of parthenogenetic reproduction in which only female progeny are produced.

18. Tolerance:

According to Painter ­(1951), it is the basis for resistance in which a host shows an ability to grow and reproduce itself, or to repair injury, despite supporting a pest population equal to that damaging a more susceptible host.

19. Trap Crop:

A small planting of a susceptible and highly attractive host, planted early in the season, or removed in space from the main crop, in order to divert attack and infestation by pests and allow for their easy destruction.

20. Virulence:

The disease producing power of a microorganism, i.e. the relative capacity of a microorganism to invade and injury the tissues of its host.

Insect Predators

Definition of Insect Predators:

The predator is defined as “an animal which feeds upon other animals (prey) that are usually smaller and weaker than itself, frequently devouring them completely and rapidly” (Copple and Martins, 1977). A predator most often is required to suck but an attack more than one prey to reach maturity.

Distinguishing Characteristic of an Insect Predator:

1. Generally it consumes more than one host individual.

2. Most insect predators move around freely in both their immature and adult stages while searching for and feeding on their prey.

3. Though many of the predators are larger than their prey, in some instances adult parasitoids may act like insect predators by feeding on and killing the host.

4. Predatory insects feed on all host stages, egg, larval or nymphal, pupal and adult.

Difference Between or Characteristics of Parasite, Parasitoid and Predator

Sr. No.	Properties	Parasite	Parasitoid	Predator
1	Size	Smaller than host	Same size as host	Large than host
2	Host	Both larva and host	Only larva and adults	Both larva and host
3	No. of host	One	One	More than one
4	Injury to host	Feed without killing	Paralyze to oviposition	Kill to devour
5	Activity	Function at low host density so efficient	Function at low host density so efficient	Function at higher host density so efficient.
6	Diurnal or Nocturnal	Diurnal/Nocturnal	Diurnal	Diurnal/Nocturnal
7	Host Specificity	Great	Great	Not so great
8	Suitability for biological control	Not suited	Best suited	Suited
9	Examples	Mosquitoes, lice bed bugs	Parasitic wasps tachinid flies	Mantids, lady bird beetles

Some Important Insect Parasitoids

1. Trichogramma:

Trichogramma spp. Are true egg parasitoids widely distributed in insect. The taxonomy of the various species is difficult, but it is now been classified that over 200 insects species belonging to 70 families and 8 orders in diverse habits are parasitized by species, subspecies and various strains of Trichogramma. Out of 26 Trichogramma species recorded in India T. japonicum and T. achea are widely distributed and are key factors for many crops pest in India. These parasitoids are mostly used against pests like sugarcane borer (Chilo spp), paddy stem borer, tomato fruit borer, cutworms, cotton bollworms etc.

A female lays about 1 to 20 eggs in one host egg depending on size of eggs but in the eggs of sugarcane bores only 1-2 eggs of Trichogramma are posited per egg. Its fecuandity varies from 20 to 200 eggs according to species and longevity of adults. Incubation period of eggs lasts for a day (16 to 24 hours). Larval period is 2-3 days, prepupal and pupal periods varies 2-3 days, and total life cycle is completed in 8 – 10 days during summer and 9 – 12 days during winter. Host eggs become dark in 3 -4 days after the parasitilization because of accumulation of urate granules unorganized eggs remain 1:1 ( M: F ). Host searching capacity is up to 3-5 meters in filed. Rice moth, coryra cephalonica is used as facitituous host for multiplication of Trichogramma in laboratory.

2. Bracon brevicornis:

It is a potent larval parasitoids of coconut black headed caterpillar. The parasitoid is an external gregarious, larval parasitoid and lays about 6 to 2 eggs pr host larvae. Its egg stage lasts for 24 to 48 hrs larval stage 5 – 6 day and pupal stage 4 to 6 days. A life cycle of the parasitoids is completed within 15 days. The pupae of the parasitoids are silvery cocoons can be stored for 10 – 15 days in refrigeration. In laboratory, the parasitoids are reared on larvae of rice moth, Corcyra cephalonica, and the adult parasitoids of Bracan brevicornis are used for releasing them in coconut plantation against target pests. Release of 40,000 to 50,000 and per r hectares week and follow such 4- 6 releases are recommended in fields.

Some Important Insect Predators

The first known use of the tactic of biological insect pest suppression was in China around 300 A.D. wherein ants were used to protect orange groves from developing wormy fruit. The red wood ants are considered important in maintaining forest insect pest population in balanced condition in 12th century. Their food consists of stages of Lepidopterous caterpillar. This is an example to be quoted for efficient facultative predator mired, Cyrtorhinus modulus have been proved as an effective predator the eggs of the sugarcane leaf hopper. Its first release was made in 1923 from Australian stock and late from Fiji and by 1923 the sugarcane hopper was suppressed.

1) Vedalia Beetle, Rodolia Cardinalis Mulsant:

This is probably the most frequent mentioned predator in classical biological control literature. It has been thoroughly received by DeBack (1974). The successful story of the Vedalia beetle against cottony cushion scale, Icerya purchasi in California on citrus has already been outlined C.V. Riley campaign. Like success in California, in has been a repeated 30-50 country around the world where this beetle has been released.
Adults of Vedalia beetle male and have a preoviposition period of 4 weeks in the summer and 1-3 weeks in the winter. The eggs are laid singly or in small cluster.

Biological Control of Weeds

Weed is a plant in the wrong place. On the other hand, weeds may be valuable plants in other situations. This fact is fundamental to a consideration of biological control. In fact the method of biological control of weed has been used when other methods found inadequate. To reduce the densities to non economic levels by either direct or indirect action of natural enemies being used.

Fundamental of Biological Control of Weed:

1. Concept of Natural Control as Related to Weed:

The competitive weed should be fast growing e.g. Stylo.

2. Kind of Natural Enemies:

Species insect feeding made preferred roots, stems, seeds and flowers.

3. Nature of Controlling Action:

Every weed cannot be controlled biological with insect.

a. Injury:

Direct feeding on vital parts like flowers, seeds or killing the plants. Indirect feeding injury increase susceptibility to diseases or secondary parasites.

b. Plant Parts Attacked:

Vital plant part should be attacked before seed formation.

4. Inter Relation of the Insect Agent and Food:

Struggle for existence, Insect attacked weed become weak and other species may become dominant. Disturbance to plant feeders by natural calamities.

5. Risk of Introduction and Host Specificity:

 Great fear of become weed feeder as feeder of economic plants.

6. Specificity Tests, Starvation:

Leaf beetle, allied to host or even more on cabbage but found not multiplied in field.

7. Nature of Infection and Prospectus of Success:

Successful weed killer should have no pest of economic plants, should attack vital plant parts, should have least natural enemies and should have fast multiplication rate.

Examples of Biological Weed Control:

1. Weed Lantana camara controlled by introduction of Telonemia scrupulosa in India (1944).

2. Prickly pear, Opuntia spp. controlled by introduction of cochineal insects, Dactylopius spp.

3. Water hyacinth controlled by weevils, Neochetina bruchi and Neochetina eichhorniae and hydrophilic mite, Orthogalumna terebrantis.

Steps in Establishing Biological Control Programmes

Following program may be followed for introduction for beneficial organism:

1) Exact Identification of Pest:

For identification of pest first recognize the occurrence of damage. Then determine the specific cause of damage and undertake precise taxonomic identification. The species names give access for availability of literature and explore the possibilities of utilizing the natural enemy of related species.

2) Origin, Geographic Distribution and Ecological Requirements:

Examine the degree of damage of the pest in homeland indicating existence of natural enemy and their importation. Determine pests’ potential important information. If the species has been the subject of successful programme earlier elsewhere, employ similar procedure e.g. Vedalia beetle used against cottony cushion scale in California. If no work has been done on the target pest, then the techniques of other related natural enemy available from similar work may be followed.

3) Host Parasitoid Lists and Other Faunal Surveys:

a. If target species is not an important pest in its place of origin it may be a god reason that density dependent natural enemy is present these to regulate population size.

b. If the species is pest its potentially useful natural enemy may have moved to new environment free from hyperparasites.

c. Search literature for previous specific studies and its natural enemies. Refer lists/catalogues/area-wise faunistic surveys for diseases, parasitoids and predators present.

4) Field Study of both Target Insect and Beneficial Organisms:

a. From literature survey, find information on location/native habitat, pest status, ecology and its natural enemies.

b. Undertake field studies in native habitat for collecting sufficient natural enemies for shipment and locate most suitable area for collection of natural enemies in large quantity.

5) Prediction of Success and Efficacy:

a. Collection preliminary information on ecology compatibility and effect of natural enemy on pest density, its behavior synchronization biotypes etc.

b. Predict certainty in the outcome of Biological insect pest suppression before. It is carries out. Success in introducing natural enemy which has proven itself before against the same target pest in a similar environment elsewhere.

6) Collection of Beneficial Organisms:

a. Collection of natural enemies for importation in short possible time. Employ minimum possible techniques to the specific pest and its natural enemy.
b. Hand collection of natural enemies of host is feasible method. But artificially dense population of host is encouraged or created in controlled area subject to exposure to the desired parasitoid.
c. Collection site need not to be at remote, exotic or inaccessible.

7) Shipment of beneficial organisms:

a. Most critical step in introduction of natural enemy programme is transportation from origin to place of introduction.

b. Necessity of providing food and water to sustain life during journey sometimes need living host/prey insects on potted plants.

c. Permit for the agencies for importation of organisms.

d. Shipment of material in a series of small shipment rather than in a single large one.

e. Containers should be strong enough to survive rough handling and prevent escape during shipment route.

f. There are wooden containers or cardboard mailing tubes, aerated plastic containers, Vacuum flasks or foam insulated containers with suitable labels for cautions of temperature extremes or adverse condition.

g. Shipment during development stages becomes easier.

h. As a part of each shipment, attack information sheet indicating, identity source, number of natural enemies and dates of collection of shipment.

8) Quarantine:

a. The purpose of quarantine is twofold. The procedure prevents the premature escape of the imported insects, and it prevents the contamination of entomophage culture by native species.

b. Adequate screening of the shipment before release to eliminate hyper parasitoids. It may be done by rearing the imported species for one or more generations under controlled conditions.

c. Admittance is usually restricted authorized personnel only.

9) Propagation:

a. Introduce large number of natural enemies.

b. Synchronies entomophage and pest life cycles with carefully timed propagative output, rearing of natural enemy all year round and storing the progeny until release.

c. Complete knowledge of life cycle, biology and behaviors, proper rearing condition and a suitable laboratory host may be factitious (unnatural) host or artificial diet.

10) Release and colonization:

a. A current trend toward the earliest possible attempt is field release.

b. Extensive laboratory propagation minimal colonization efforts.

c. Incomplete understanding of the host-parasitoid or prey-predator relationship may lead to poor adaptation of natural enemy.

d. Alternate host, required food supplies of nectar or polled for the adults may be missing for the introduced natural enemy which eater establishment of entomophage.

e. Proper time of introduction of natural enemy against target pest of univoltine type.

f. Predators should be released with greatest assurance of mate and early reproduction.

g. Select promising site for introduction based on preceding information for easy and natural spread.

h. Colonization by installation of field cages i.e. for predators to minimize initial spread / dispersal and protect against native competitor species.

i. Predict weather conditions like frosts, heat waves, heavy rains / winds, bright sunshine which causes high mortality of colonized natural enemy.

j. Release are best made in early mornings or late evening when light levels are subdued, temperatures are lower and humidity is high.

k. Release larger colonies at few point, multiple induction quickly regulate pest spectrum.

l. Greatest success with smallest individual releases in the stable environment.

11) Follow-up Recoveries:

a. Determination of establishment of introduced natural enemy and its rate of dispersal.

b. Carry out making field observation and collection in and near the sites of release or by visual determination in the field after the sites or release or by visual determination in the field after one generation or dissect parasitized host or by rearing of adults from field collected host material.

c. Recoveries:The first instance of recovery indicate temporary or initial establishment of natural enemy. The second or third instance indicate permanent establishment only if it is recovered in three successive year after its release.

12) Evaluation:

Assessment of effectiveness of natural enemy by careful and continuous monitoring of increase and spread of introduced entomophages.

It involves 3 ways.

a. Qualitative analysis:

By frequent extensive sampling observation of the progress and spread of introduced species and apparent cause effect relationship to decline pest populations.

b. Experimental exclusion procedure:

By comparing the population density of the pest in the absence of newly introduced natural enemy with that in presence of the introduced natural enemy with that in the presence of the introduced species.

c. Quantitative mathematical analysis:

It is best proof of success or failure. it involves development of extensive life tables of pest both before and after the introduction of natural enemy.

Future Needs of Biological Pest Suppression

In future, Non Government Organizations (NGOs) should to expedite the pilot projects on mass production of same biotic agents like Trichogramma which have great potential to control pest like sugarcane borers, maize, sorghum, paddy cotton bollworms moths etc. predators such as Chrysopid and Coccinellids for aphids, mealy bugs on cotton, tobacco, grape guava and citrus guava and citrus similarly pathogens like NPV and saprophytic fungi and produce toxins (Gliotoxin and Varadin) which will the rute root disease of pulses and oilseeds.

Government may also consider the following suggestions for future works which may helps farmers in adopting bio control technology:

1. Popularization of literature through local languages.

2. Increasing finance to other bio control projects beside AICRPBC sanctioned by ICAR, New Delhi, and Department of Science and Technology and DBT, Government of India.

3. Judicious as well as restricted import of biotic agents from other countries.

4. Emphasis on exploration of indigenous biotic agents.

5. Preparation of ‘Field guide for biotic agents’ along with their visible stages and natural hosts.

6. Establishment of commercial factories to ensure supply of potential biotic agents.

7. Establishment of National Institute on Conservation of Biotic Agents along with network at district level.

8. Studies on biotic agents in relation to intercropping, cultural practices and other forms of organic farming.

Current problems with the use of chemical insecticides and emphasis on low impact sustainable agricultural have pushed the microbial agents to the fore front for use in pest management. However, microbial pesticide has not been economically competitive with chemical insecticides, primarily due to their host specificity. The relatively slow speed with which microorganism kill their hosts has hampered their effectiveness as well as acceptance by potential users. A wide range of environmental factors affects the efficacy of microbial pesticides. Development of resistance to viruses and Bt is a matter of serious concern. However, the use of both naturally occurring and genetically engineered microorganisms may increase the effectiveness against the less susceptible species.

Place of Insect in Animal Kingdom

Animal Kingdom is Divided in 10 Phyla:

1. Protozoa e.g. Amoeba
2. Porifera e.g. Sponges
3. Coelenterata e.g. Jelly fish
4. Platyhelminthes e.g. Tapeworm
5. Nemathelminthis e.g. Roundworm (Nematodes)
6. Annelida e.g. Earthworms
7. Arthopoda e.g. All insects
8. Mollusca e.g. Snail & Slugs
9. Echinodermata e.g. Star fish
10. Chordata e.g. Frog

Characters:

1. Body metamerically segmented with jointed limbs.
2. Body segments are grouped to form head, thorax and abdomen.
3. Body covered with exoskeleton made up of chitin, which is moulted at definite intervals.
4. Bilaterally symmetrical animals.
5. Cilia are absent. (except in peripatus)
6. Aquatic forms breath with gills while, terrestrial forms by air tubes called trachea.
7. Body cavity called haemocoel.
8. Compound eyes are present.
9. Nephridia absent.
10. Sexes are separated.

There are Six Classes of Phylum Arthropoda:

1. Onycophora e.g. Peripatus
2. Crustacea e.g. Crabs, Prawns, Lobsters
3. Chilopoda e.g. Centipedes
4. Diplopoda e.g. Millipeds
5. Arachnida e.g. Spider, ticks, mites
6. Insecta (Hexapoda) e.g. All Insects

Class: Insecta or Hexapoda:

Characters:

1. Body is segmented and invested with chitinous exoskeleton.
2. Body is divided into three regions viz., Head, Thorax, and Abdomen.
3. Head bears a pair of antennae and compound eyes and the mouthparts.
4. Thorax carries three parts of legs and two pairs of wings in adult stage.
5. Only one pair of jointed appendages is born on the body segment.
6. Abdominal appendages on 8th and 10th abdominal segments are modified for mating.

Modern Classification is Based on the Following Criteria According to Imms:

1. Presence and absence of wings and their features.
2. Mouth parts and their modifications.
3. Morphological characters of all stages of insects.
4. Types of metamorphosis.
5. Characters afforded by antennae and tarsi.
6. Embryological and post-embryological evidence.
7. Evidence of fossils.
8. The details of life history.

General Organization of an Insect Body

The body of an insect is covered with a hard chitinous cuticle (exoskeleton) which project, it from mechanical injury and prevent excessive loss of moisture. The body is segmented i.e. composed of series of successive rings, called segments.

Metameres/Somites: Where these are movable, they are separated by flexible inter-segmental membranes. The body is divided into three distinct regions viz., the head, thorax and abdomen.

Head: The head consist of six embryonic segments. The head is concerned with feeding and sensory perception. It bears a pair of antennae, a pair of compound eyes, three ocelli and the mouth parts. Head is highly sclerotized. The sclerotized capsule manus the appendages is called cranium.

Compound eyes are located at dorso-lateral sides of the head. Each eye consists of a number of separate visual elements called ommatidia. Compound eyes are useful in image perception ocelli are situated in between the compound eyes. There simple eyes. They are sensitive to light intensity but not useful in image perception. Antennae are paired segmental appendages that articulate with the cranium between the compound eyes. Antennae are flexible and are sensory in function. Mouthparts consist of labrum (upper lip), labium (lower lip), mandibles and maxillae (two pairs of jaws) and hypopharynx (tongue like organ).

Head is connected to thorax by a membranous region called the neck or Cervix. The cervical membrane is quite flexible and allows movement of the head.

Thorax: Thorax consists of three segments, viz., pro, meso and metathorax. Each segment consists of a dorsal region called the tergum (notum), ventral region called the sternum and lateral region pleuron on each side of body. Each thoracic segment bears a pair of segmented legs. The meso and metathorax each bears a pair of wing which are collectively called as pterothorax. Mesothoracic wing are called forewings and metathoracic wings are called hind wings. Thorax is mainly concerned with locomotion.

Abdomen: The abdomen consists of eleven segments, although it is difficult to distinguish all of them due to telescopic arrangements of the segments. The successive segments are joined by inter-segmental membrane called conjunctiva which makes the abdomen flexible, which is required during copulation and oviposition. Each abdominal segment usually composed of a dorsal (tergum) and ventral (sternum) plants, there is no pleuron. The tergum is connected to the sternum by a thin membrane. Posterior abdominal segments are modified for the purpose of mating and oviposition. The triangular dorsal plate of eleventh segment is call epiproct and paired lateral plates are called paraprocts. A pair of short unsegmented cerci is present between the epiproct and paraprocts. They are sensory in function. Anal openi9ngs are found immediately below the epiproct.

An oval shaped transparent auditory membrane, tympanum is found laterally on either side of the first abdominal segment e.g. grasshopper. There are eight pairs of openings called spiracles present on lateral sides of thoracic and abdominal segments, which are concerned with respiration.

The Heads of Insects are Oriented in One Three Ways

1. Hypognathous: The long axis of the head is vertical i.e. at right angle to the long axis of the body. The mouthparts point downwards e.g. grasshopper, cockroach etc.

2. Prognathous: The long axis of the head is horizontal and in line with the long axis of the insects body. The mouthparts are directed forwards e.g. Stick insect, soldier caste of termites etc.

3. Opisthognathous: The head is reflexed ventrally so that the mouth parts are directed backwards between the coxae of the front legs e.g. Red cotton bug.

Antennal Structure and its Modifications

Insect Antennae:

There is only pair of antennae on the head of an insect (except in Proturans where antennae are absent). Each consists of a basal segment called the scape, follow by the pedicel and the remaining part is called the flagellum. The scape is inserted into a membranous region of the head wall and pivoted on a single marginal point, called the Antennifer.

Function:

The main function of antennae is sensory which is modified according to use and need of insect. Antenna is an organ of smell and touch. It is useful to detect chemicals including food and pheromones. Also perceives humidity changes, variation in temperature, vibration, wind velocity and direction. It is useful for hearing in mosquitoes and communication in ants. Occasionally useful to clasp the mate (e.g. flea) and grasp the prey.

Types:

1. Setaceous (Bristle-like): Size of the segments decreases from the base to apex e.g. cockroach.

2. Filiform (Thread-like): Segments are usually cylindrical in shape. Thickness of segments remains same throughout e.g. Grass hopper.

3. Moniliform (Beaded): Segments are either globular or spherical with prominent constrictions in between e.g. Termite, Ground beetle etc.

4. Serrate (Saw-like): Segments have short triangular projections on one side e.g. Mango stem borer.

5. Unipectinate (Comb-like): Segments with ling slender processes on one side e.g. Sawfly

6. Bipectinate (Double-comb-like): Segments with long slender lateral processes on both the sides e.g. Silkworm moth

7. Clavate (Clubbed): Antenna enlarges gradually towards the tip e.g. Butter fly.

8. Capitate (Knobbed): Terminal segments become enlarged suddenly e.g. Khapra beetle, weevils etc.

9. Lameliate (Plate-like): Antennal tip is extended laterally on one side to form flat plates e.g. Dung roller.

10. Aristate (Bristle like): Antenna is just three segmented. The terminal segment enlarges. It bears a conspicuous dorsal bristle called arista e.g. House fly

11. Stylate: Antenna is just three segmented. The terminal segment bears a style like process e.g. Jassid

12. Plumose (Feathery): Antenna is feathery with much long hair, in whorls at the junction of flagellomeres e.g. Male Culex mosquito. A mass of sense cells collectivity called Johnston’s organ (hearing organ) present in pedicel of male mosquito.

13. Pilose (Hairy): Antenna is less leathery with fewer hairs at the junction of flagellomerer e.g. female Culex mosquito.

14. Geniculate (Elbowed): The scape is long. The remaining segments are small and are arranged at an angle to the first, resembling an elbow joint e.g. Honey bee, wasp etc.

Chewing and Biting Type (e.g. Cockroach)

Insect feed on plants and animals in diverse ways and their mouthparts have become modified for these purposes. They are mainly two types viz. Mandibulate (feeding mainly on solid food) and Haustellate (feeding mainly on liquid food).

Chewing & Biting Type: The basic and most primitive type of mouthparts present in grasshopper, cockroach and beetles. In order of appearance, from anterior to posterior, chewing mouthparts consists of a single labrum (upper lip). A singly structure, the hypopharynx (tongue like organ) is located centrally. The inner surface of the labrum is referred to as the epipharynx, an area frequently membranous and inconspicuous.

i. Labrum: It is a flap like bilobed structure attached to the clypeus by an articular membrane. It helps to guide the food into the mouth and also holds the food in position so that mandibles can act on it. Epipharynx is identified as a swollen area of the ventral surface of the labrum, which is an organ of taste.

ii. Mandibles: They are also called as primary or true jaws and concerned with chewing and grinding the food. They are hinged to the cranium by anterior and posterior articulations. They have transverse movement produced by abductor (outer) and adductor (inner) muscles. They are heavily sclerotized and are toothed o their inner border. Distal teeth are sharply pointed and area called incisors or cutting teeth. The proximal teeth are called molar or grinding teeth.

iii. Maxillae: They are called as secondary jaws or accessory jaws. The basal segment, known as the cardo, joins the maxilla to the head. This is joined to the central body of maxilla, the stipes. On the outer side of the stipes is a more or less distance sclerite known as the palpifer to which the palpus is attached. Antennae like five segmented Palpi, bears tactile hairs and also probably organs of smell or taste. On the distal end of the stipes there are two lobes. The outer lobe is called galea and the inner lobe lacinia which is toothed. May be employed for grasping/cutting/chewing food. Whenever these two distinct lobes are fused together to form a single lobe (e.g. Coleopterous larvae) it is termed as Mala.

iv. Labium: It closes the mouth cavity from below or behind. It is informed by fusion of two primitive segmented apopendages like maxillae. It consists of three median sclerites viz. submentum (large basal sclerite), mentum (middle sclerite) and prementum (apical sclerite). On the lateral side of the prementum, there are two small lateral sclerites called palpiger bearing seven segmented labial Palpi. Distally prementum bears two pairs of lobes. The outer pair is called paraglossae and inner pair glossae. Both pairs when fused together to form a median lobe (e.g. Grasshopper), it is termed as Ligula.

Instructions for the Dissection:

Hold the head capsule between the thumb and the index-finger and gently press it. All the components of mouthparts will be seen distinctly. Remove labrum, right & left mandibles, right & left maxillae, hypopharynx and labium and mount them in a drop of glycerin on a slide. Place a cover slip over it and examine under a microscope.

Chewing and Lapping Type (e.g. Honey bee)

This type of mouthparts are possessed by Honey bee wherein, the Labrum & Mandibles remain more or less similar as that of the Generalized type, whereas the other components viz. (Maxillae & Labium) are greatly modified Labrum. It is narrow and quite simple.

Mandibles: They are blunt dumble shaped and are not toothed. They are not used for feeding but are useful for moulding wax into cells for comb (next) building.

Libium: The glossae are greatly elongated to form a hairy, flexible tongue. The glossa terminates into a small circular spoon shaped lobe called flabellum, which is useful to lick the nectar. Labial palms are elongate and four segmented.

Maxillolabial Structures: Maxillobial Structurev are modified to form the lapping tongue. The tongue unit consists of the two galeae of maxillae, two labial Palpi and elongated flexible hairy glossa of labium.

Feeding Mechanism: The galeae fit tightly lengthwise, against the elongated labial palps and they in turn roof over the elongated glossae (tongue) to form a temporary food channel through which saliva is discharged. The tongue (glossae) is trusted into flower, which gets smeared with nectar. It is then retracted between labial palps & galeae. Nectar is then squeezed by galeae and is deposited in the cavity formed by the paraglossae. Accumulated nectar is then drawn into oesophagus by the pharyngeal pump.

Piercing and Sucking Type of Mouth Parts (e.g. Red Cotton Bug)

There are two distinct operations are involved in this type of mouth parts (i) piercing and (ii) sucking. The insects having such type of mouth parts are different plant bugs, aphids, jassids, whiteflies, mealy bugs, scale insects etc. they feed on liquid food material like plant cell sap. The principal parts, which are modified to form piercing and sucking mechanism in red cotton bug, are as follows

1. Labium: It is a long, four-segmented beak like hollow structure called as rostrum or proboscis. This enclosed 4 needle like structures called as stylets, in the dorsal groove. Labium, does not take part in piercing the tissue and sucking the cell sap.

2. Mandibular and Maxillary Stylets: Lying inside the dorsal groove of the labium, are four, very sharp chitinous stylets, which are responsible for piercing the plant tissues and sucking up the cell sap.

The outer pair constitutes the Mandibular stylets which are usually serrated at the apex. The inner pair constitutes the maxillary stylets, which tapers to a fine point. Each maxillary stylet is double grooved along its inner face. When such two stylets fit tightly against each other two microscopic closed types are formed. The dorsal tube is the suctorial tuber while the ventral food channel and communicates with cibarial sucking pump. The ventral tube is ejection channel or salivary channel for ejecting the saliva. Maxillary palps are absent. Each Mandibular and maxillary stylets alternately have downward and upward movement for the purpose of piercing due to retractor and protractor muscles arising from the respective Mandibular and maxillary plates. All the four stylets normally cling together appearing like a single bristle. All the four stylets pierce the tissues.

1. Labrum:

Labrum is a short, triangular, flap like structure, which covers the labial beak at its base.

2. Hypopharynx: is highly specialized greater protion of it forms the floor of cibarial sucking pump which is provided with strong dilator muscles arising from the clypeus.

Feeding Mechanism:  At rest, proboscis is always held parallel to the ventral side of the insect body. When insect is about to feed, the proboscis is stretched and stylets are released out from the labial groove. Then the proboscis gets looped behind so as to allow the stylets to penetrate in to plant tissues.

The Mandibular stylets pushing first followed by the maxillary stylets, alternately and it rapid rate, thrust themselves into the epidermis till they reach the cell sap. Saliva is then poured into the plant tissues from the salivary glands by means of salivary channel. This saliva also acts as lubricant in between the sliding Mandibular and maxillary stylets. The cell sap is then sucked by means of suction canal into the mouth cavity by the action of cibarial pump. The cibarial muscles are powerful, which when contract, a vacuum is created in the mouth cavity and cell sap slowly rises up through the food channel because of capillary movement and passes into the oesophagus after the relaxation of dilator muscles.

Sponging Type of Mouth Parts (e.g. Housefly)

The prominent fleshy and retractile proboscis consists mainly of the labium and is attacked in elbow – like form to the elongated head. The proboscis can be differentiated into basal rostrum and distal haustellum. The proboscis is grooved on its anterior surface, within this groove lie the labrum-epipharynx (enclosing the food canal) and slender hypopharynx (containing the salivary canal). Mandibles are absent. The maxillae have evidently become fused with the fleshy elbow of proboscis, and only the prominent single segmented maxillary palpi remains.

The end of the proboscis is enlarged, sponge like and two-lobed which acts as suction pads. They are called labella. The surfaces of labella are transverse by capillary canals called pseudotracheae, which collect the liquid food and convey it to the food canal. These insects often spit enzyme-containing saliva onto solid foods to liquefy them and then sponge up the mixture.

Feeding Mechanism: When labella are pressed against the exposed liquid material, the pseudotracheae absorb it and get filled with by capillary attraction. The liquid is then collected at a point on the labella wherein these tiny channels converge. From this point the liquid is then drawn up through food channel formed in-between the two stylets viz. labrum epipharynx and hypopharynx.

Instruction for Dissection of Honey Bees, Red Cotton Bug and House Fly

Instruction for Dissection of Honey Bees:

Cut the head from the thorax, Hold the head between the thumb and the index finger with the mouthparts facing you. Remove each mandible by exerting outward pressure at the base with a needle. Change the position the head, so that its posterior side faces you in an inverted position. Make it flaccid by applying some pressure. Remove the maxilla-labial complex by exerting upward pressure at its base with a needle. Mount the mouthparts in glycerin on a slide and remove the extraneous tissues from them. Place a cover-slip over them and examine under a microscope.

Instruction for Dissection of Red Cotton Bug:

Cut the head from the thorax. Hold the head between the thumb and the index-finger and make it flaccid by applying some pressure. Place it on a microscope slide and moisten the proboscis with a drop of water. Press the proboscis gently at various places with the help of a needle till the stylets come out of the labial sheath and get disengaged. Mount the mouthparts in glycerin on a microscope slide and arrange them as shown in the diagram. Place a cover them and examine under a microscope.

Instructions for Dissection of House Fly:

Cut the head from the thorax. Hold the head between the thumb and the index finger with the posterior side of the proboscis facing you in an inverted position. Remove the proboscis by exerting upward pressure at its base with a needle. Place the proboscis in glycerin on a microscope slide and remove the extraneous tissues from it. Place a cover slip over it and examine under a microscope.

Structure of Thorax and its Processes

Thorax consists of three segments viz. Prothorax, mesothorax and metathorax. Each of these segment differentiated into dorsal region called tergum or notum ventral region called sternum and lateral region called pleuron on each side. The sclerites composing these respective regions termed as sternites and pleurites.
The sclerites of a thoracic segment:

1. Tergite form the dorsal Notum is divisible into – (A) Pre-scutum (B) Scutum (C) Scutellum.

2. Sternite constitutes the ventral side and is divisible into – (A) Pre-sternum (B) Basi-sternum (C) Sternellum.

3. Pleurite on each lateral side is divisible into – (A) Episternum (anterior) (B) Epimeron (posterior)

Types of Insect Wing

1. Membranous: e.g. Dragons Fly Honeybee and Termites: Wings are thin and transparent. They are supported by a system of tubular veins. They are useful in flight.

2. Fringed: e.g. Thrips: Wing lamina is usually reduced in size. Wing margins fringed with long setae. These insects literally swim through the air.

3.  Haltere: e.g. Hand Wings of Housefly: Wings are modified into small knobbed vibrating organ called halters, which act as balancing organs and provided the needed stability during flight.

4. Scaly: e.g. Moths and Butterflies: Wings are covered with scales which are unicellular, flattened outgrowths of the body wall. Scales are responsible for colour. They are important in smoothening the airflow over wings and body. They also insulate the insect against cold.

5. Tegmina: e.g. Forewings of Grasshopper and Cockroach: Wings are leathery or parchment-like. They are protective in function. They are not useful for flight.

6. Elytra: e.g. Forewings of Beetles and Weevils: Wing is heavily sclerotized and thick. Wing venation is lost. Wing is tough and protective in function. It protects the hindwings and the abdomen. It is not used for flight. In flight they are kept at an angle to allow free movement of the hindwings.

7. Hemelytra: e.g. Red Cotton Bug: The basal half of the wing is thick and leathery. The distal half is membranous. They are protective in function and not involved in flight.

Insect Wing Coupling

In primitive Pterygota fore and hind pair of wings moved independently of each other e.g. Isoptera and Odonata. Higher pterygotes have attained virtual dipterous by coordinated wing movements. Both the pairs of wings move synchronously.

1. Hamulate: A row of small hooks called hamuli are present on the costal margin of the hindwings. These hooks catch the folded posterior edge of fore wings e.g. Honey bee.

2. Amplexiform: A linking structure is absent. Coupling is achieved by broad overlapping of adjacent margins e.g. Butterflies.

3. Frenate: e.g. Fruit sucking moth.

i. Male Frenate: Hindwing bears near the base of the costal margin a group of shout bristles called frenulum which is held by a curved process, retinaculum arising from sub-costal vein found on the under surface of the forewing.

ii. Female Frenate: Hindwing bears near the base of costal margin a group of stout bristles (frenulum) which lies beneath the extended forewing and engages there in a retinaculum formed by a patch of hairs near the cubitus.

In Aphids various small hooks present at margins of forewing and hind wind.

Type of Insect’s Legs

The insect legs are paired, hollow, more or less cylindrical and jointed outgrowths of the thoracic segments.

A typical leg consists of the following six segments in sequence.
1) Coxa – Coxae
2) Trachanter – Trochanters
3) Femur – Femore
4) Tibia – Tibiae
5) Tarsus – Tarsi
6) Pretarsus – Pretarsi

The Articulation of legs: - The coax articulates with the pleurite at the coxal process and also with the trochantin (articulatory sclerite present near base of coax in primitive insect). The coxal process is situated at the ventral extremity of the pleural suture.

1. The Coxa: It is divisible into coxa-vera (anterior lobe) and meron (posterior lobe)

2. The trochanter: It is most conspicuous and largest segment in many jumping insects.

3. The femur: It is most conspicuous and largest segment in many jumping insects.

4. The Tibia: It is Slender and equals length of femur. Near its distal extremity, carries one or more spurs. In Hymenoptera, the apical and enlarged spur of the anterior tibia fits against semicircular pit of the first tarsal segment through which the antennae are passed and cleaned.

5. The tarsus: In primitive insects it is only one segmented (in Protura & Diplura). But usually it is divided into five segments (tarsomeres). The sub segments do not move independently but only the tarsus as a whole moves.

6. The Pretarsus: Beyond the tarsus, there are several structures collectively known as Pretarsus. Tarsus terminates in a strongly curved claw in Collembola and Protura.

In most insects the claws are paired and between them, on the ventral side, a median unguitractor plate to which flexor muscle of the claws is attached supports the pretarsus. In front of and above this plate the Pretarsus expands into a median lobe or arolium. Among Diptera there are two lobes or pulvilli lying below the claws, often with arolium between them or in place of an arolium, median bristle called empodium.

Log pads (covered with tenant hairs) enable insects to climb smooth and steep surfaces. While claws give grip while walking on rough surface

Modification of Insect’s legs

1. Ambulatorial (Walking leg): e.g. Fore and middle legs of cockroach. Femur and tibia are long. Legs are well developed similar in form.

2. Cursorial (Running leg): e.g. All three pairs of legs of Ants. Femur in not swollen. All the legs are long.

3. Saltatorial (Jumping leg): e.g. Hind leg of grasshopper, field cricket, Trochanter is fused with femur. Hind femur is enlarges.

4. Scansorial (Clining leg): e.g. All three pairs of legs of head house. Tibia is stout and at one side bears a thump like process. The tarsus is single segmented. There is a single large claw that usually fits against a thumb-like process, which forms an efficient mechanism for hanging on to the hairs of host.

5. Fossorial (Digging leg): e.g. Fore legs of mole cricket. Femur is shout. Tibia is short and shout and bears distally two or three strongly printed tines. The first two segments of tarsus are also produced into strong tines. The first two segments of tarsus are also produced into strong tines. Tympanum is present on fore mantids.

6. Raptorial (Grasping leg): e.g. Fore legs of preying mantids. Fore legs are of no use in locomotion. Coxae elongated to give an extended reach to capture the prey. The femur is large and groove when it snaps down over the prey. Tarsus consists of five tarsomeres.

7. Natatorial (Swimming leg): e.g. Hind legs of water bug or water. Beetle, Femur, tibia and first four tarsomeres are all broad and flattened. Their edges are provided with flattened setae. The hind legs serve as oars.

8. Sticking leg: e.g. All the three pairs of legs of housefly.
Pretarsus consists of a pair of lateral adhesive pads called pulvilli and a pair of claw. Arolium is absent. But a median spine like structure called campodium is present. The pulvilli are covered with dense mats of tiny glandular hairs called tenant hairs. Secretions of these glandular hairs are helpful in clinging to smooth surfaces and to walk upside down on the ceiling.

9. Basket-like leg : e.g. Legs of dragonfly and damselfly
Legs are situated just being the head and are anterior in position. Legs are spiny and closely placed which are useful in seizing the prey during flight. Legs are not useful in locomotion.

10. Foragial leg: (Pollens collecting and carrying leg) e.g. legs honey bee.
a. Eye brush: Hairs on tibia useful to clean the compound eyes.
b. Antenna cleaner: Velum is a movable clasp present at distal end Tibia. Antenna c. c. comb semicircular notch lined with small spines.
d. Pollen brush: Bristles on basitarsus from the pollen brush which is useful to collect pollen from the head and mouth parts.

Role of Insects Leg

Middle Leg:

Pollen brush: Stiff hairs on basitarsus useful to collect pollen from middle part of their body.

Tibial spur: At the distal end of the tibia a movable spur is present which is useful to loosen the petals of pollen from the pollen basket of hind legs and to clean wings and spiracles.

1. Hind Leg:

a. Pollen basket: The outer surface of the hind tibia is concave. The edges of the depressed area are fringed with long hairs. Pollen basket used to carry larger load of pollen and propolis.

b. Pollen packer (Pollen press): Pectin is a row of stout bristles at the distal end of tibia. Auricle is a small plate fringed with hairs at the end of basitarsus. Pollen packer is useful to load pollen in pollen basket.

c. Pollen comp: Stiff spines present on the inner side of hind basitarsus. It is used to collect pollen from middle legs and from posterior part of body.

2. Prolegs: Prolegs  or false legs or pseudo legs: e.g. abdominal legs of caterpillar. Prolegs are thick, fleshy and non-segmented. The tip of proleg is called planta upon which crochets (hooks or claws) are present. It helps to cling to surface.

Central Nervous System of Cockroach / Grasshopper

I. Brain or Supra Oesophageal Ganglion:

It is anterior most ganglionic mass above the oesophagus between the supporting apodermes of the tentorium. It comprises of the following components.

1. Protocerebrum: Represent the fused ganglia of the acron and preantennal segment. It is the anterior most and largest part of the brain consists of protocerebral lobes and optic lobes. It innervates the compound eyes and ocelli.

2. Deutocerebrum: It is the second or central part of the brain. Represent the fused ganglia of the antennal segment. It innervates antennae.

3. Tritocerebrum: It is the posterior part of the brain formed by the ganglia of the third or intercalary segment of the head. Innervates labrum and unite the brain with forntal ganglion.

Circum-oesophagus and joining supra-oesophageal ganglion with sub-oesophageal ganglion

II. Sub-oesophageal Ganglion: It is oval shaped, lines below the oesophagus in the head region. It is formed by the fusion of the ganglia of the Mandibular, maxillary and labial segments. It gives off paired nerves supplying their respective appendages.

III. The Ventral Nerve Cord: Consists of series of ganglia lying on the floor of thorax and abdomen.

1. Thoracic ganglia: The first three ganglia are situated one in each of the thoracic segment called thoracic ganglia. It controls the locomotory organ. Each ganglion gives off two pairs of principal nerves, one of which supplies the general musculature of the segment and the other innervates the muscles of the legs and wings.

2. Abdominal Ganglia: Six in number, lie in the abdomen. Each abdominal ganglion gives off a pair of principal nerves to the muscles of its segment.

3. Connective: These are two longitudinal cords, joining one pair of ganglia with those preceding and succeeding it.

4. Commissures: These are the transverse fibers; unite the pair of ganglia of the system.

Instructions for Dissection for Study of Central Nervous System of Cockroach

Cuts open the cockroach as instructed earlier. Remove the alimentary canal and remaining fate bodies and observe the ventral nerve cord. Trace the three pairs of thoracic ganglia by pulling apart the legs and removing the muscles. Remove the viscera, fat bodies and trachea and observe the abdominal ganglia. Locate the brain which is situated in the head, in between two eyes and below the epicranium. Hold the head in hand and take cuts onto lateral sides outside the antennae. Insert the angular scissor and cut the epicranium transversely. Lift up the front part of head capsule and remove it by scraping with arrow headed needle and observe the bilobed brain. Cut open the neck and part of head capsule up to the brain and separate them from the brain. With the help of forceps find out the hard part of occipital ring, break it and trace the sub-oesophageal ganglion. Mount the system on black back-ground and observe the brain, sub-oesophageal ganglion, thoracic ganglia and abdominal ganglion, thoracic ganglia and abdominal ganglia.

Structure of Thorax and its Processes

Thorax consists of three segments viz. Prothorax, mesothorax and metathorax. Each of these segment differentiated into dorsal region called tergum or notum ventral region called sternum and lateral region called pleuron on each side. The sclerites composing these respective regions termed as sternites and pleurites.
The sclerites of a thoracic segment:

1. Tergite form the dorsal Notum is divisible into – (A) Pre-scutum (B) Scutum (C) Scutellum.

2. Sternite constitutes the ventral side and is divisible into – (A) Pre-sternum (B) Basi-sternum (C) Sternellum.

3. Pleurite on each lateral side is divisible into – (A) Episternum (anterior) (B) Epimeron (posterior

Insect Orders: Thysanoptera

Thysanoptera (Physapoda) Thysanos : a fringe, pteron-wing also termed as e.g. Thrips.

Economic Importance: Fringed winged insects, majority are crop pests some of them act as vectors of bacterial/fungal/viral plant diseases.

Characters:

1. Small or minute slender bodied insects.
2. Antennae short 6 to 10 segmented.
3. Mouth parts asymmetrical rasping and sucking with maxillary and labial palps. Right mandible absent. Left mandible and maxillae modified into stylets.
4. Prothorax free and well developed.
5. Tarsi 1 or 2 segmented, each with a terminal protrusible vesicle (hence the name “Physapoda”).
6. Wings when present very narrow with greatly reduced venation and long marginal setae.
7. Cerci absent.
8. Metamorphosis accompanied by inactive pupa like instars.

The order has been classified into two sub-orders:

I) Sub-order: Tubulifera:

Characters:

Ovipositor absent 10th abdominal segment usually tubular wings without microtrichia, veins absent or with one vestigial vein.
Family Phlaeothripidae, Olive thrips

II) Sub-order – Torebrantia:

Characters:

Ovipositor saw like apex of abdomen conical in female and bluntly rounded in male, wings usually covered with microtrichia fore wings with at least one longitudinal vein reaching to apex.

Family: Thripidae – e.g. Onion thrips

Instructions for Dissection for Study of Male Reproductive System of Cockroach

Cut open the cockroach as described earlier. Separate the fat bodies on the side of the anterior region of abdomen and locate the bunch of testis, which can be distinguished by its different shape. Separate the alimentary canal slowly and remove it by cutting at the crop at one end and at the rectum at another. Detach lobes of testis from the sterna along with fat bodies with the help of needle and forceps. Pin down the whole mass of testis on both the sides. Gently shake the fat bodies near the base of the mass and observe vas deferens running as a thin straight whitish line. Separate the fate bodies with forceps and trace the vas deferens and lobes of the testis. Remove the remaining fat bodies in the abdomen and expose milky white, much branched mushroom gland. Remove the ventral nerve cord and observe club shaped conglobate. Trace the ejaculatory duct which is milky white in colour observe a pair of testes, a pair of vas deferentia, mushroom gland, ejaculatory duct and conglobate gland.

Male Reproductive System of Cockroach/Grasshopper

Male Cockroach: Antennae are longer than body and third segment shorter than second. Mesosternum is partly divided and ninth sternum is visible. Abdomen is narrow and a seventh sternum undivided. A pair of anal styles (clasper) is present.

The Male Reproductive Organs:

i. Testes: They are a pair of faintly whitish gonads each is termed testis, which occupies dorsolateral abdominal segments. Each testis consists of 30-40 small rounded vesicles (sperm-tubes) the testicular follicles in three or four groups but arranged in a longitudinal series.

ii Vasa deferentia: These are a pair of ducts each is termed was deferens and arise from the testis as very thin whitish tubes, they continue posterioventrally beneath the rectum. They unite at a short distance into the ejaculatory duct.

iii. Vesicula seminalis: Spermatozoa on their way to ejaculatory duct are retained for sometime.

iv. Ejaculatory duct: It is a common duct, of vasa deferentia and leads backwards to the phallus.

v. Accessory glands: These are the glands associated with reproduction and comprises of the following:

viiMushroom gland (Utricular gland): It consists of numerous whitish tubules lying above the ejaculatory duct.

viii. Conglobate (phallic) Gland: It is a large elongate sac like structure lies beneath the mushroom gland and ejaculatory duct. It opens by the side of male gonopore. The secretion of accessory glands is mixed with the spermatozoa (or in some insects, it concerned with the formation of spermatophores).

Metamorphosis

On hatching from eggs of the insects do not resemble their parents. To attain the maturity and to become adults, these young ones have to pass through different stages of development assuming distinctly different morphological forms. These morphological forms may not be similar to their parents. Thus, morphological forms may  not be similar to their parents. Thus, the conspicuous changes inform and appearance assumed by the insects between hatching and maturity is called metamorphosis. This is a characteristic phenomenon in the life of majority of winged insects. Exceptions however, do occur in the primitive or primarily wingless and secondarily wingless insects. The group of such insects, which do not undergo metamorphosis, is called Ametabola. In this group the development of insects occurs through three stages viz., egg, young ones and adult. The young one looks like their parents in its all body characters. The only difference between young ones and adults is that the young one are smaller in size and shape while the adults possess functional reproductive organs. In this group of insects neither the young ones nor the adult’s stages show any presence of even rudiments of wings in the course of development and in their ancestral development. They are therefore; called primarily, wingless insects e.g. Silver fish, Spring tails, Compodea, Proturans etc.

The growth of an insect is a continuous process while the integument or body wall of an insect forming the exoskeleton is rigid and it is only possible of insect to put on growth by casing off the old cuticle periodically. This process of periodical shedding of old cuticle is called ecdysis or moulting and old skin cast off by insect is called exuviae. The form attained by the insect between two successive moulting is called instars. There are several such instars in the immature stage of insects. (4 to 8 moults) the total period between any two moulting is called a stadium.

Significance of Metamorphosis:

1. It helps the insects to tie over unfavorable climatic conditions by entering into hibernation, aestivation and or diapauses.

2. It helps the insects to accommodate growth by periodical shedding of their old cuticle and by formation of new cuticle.

3. It helps the insects to reduce or avoid competition for food amongst themselves by either entering into inactive stage or by acquiring different feeding habits & habitats.

4. It helps the insects as a protective adaptation by way of camouflaged/mimicry i.e. resemblance to the nature.

5. It also serves as important aspect in classification of insects.

Types of Metamorphosis

1) Incomplete Metamorphosis or Direct or Simple Metamorphosis:

The group of the insects undergoing this type of metamorphosis is also called Hemimetabola. Insects under this type complete their postembryonic development without assuming much striking morphological changes. There are three stages in the life of these insects’ viz. egg, nymph and adult. The young ones on hatching from eggs are called nymphs. These nymphs resemble their parents very much in their structure of body (mouth parts, simple and compound eyes, antennae, legs etc). Similarly they have the same mode of life, feeding habits, food and habitat. The difference between the nymphs and adults is that the nymphs do not process wings and reproductive organs until they turn into full-grown adults. Besides, nymphs are smaller in size and shape.

The wings develop gradually from a small wing pads in the nymphs to a fully developed functional wings in matured adults. This type of metamorphosis is therefore, also called gradual metamorphosis. This wings development takes place externally and hence this group if insect is called Exopterygota. The nymphs grow in size and shape by the process of moulting and the successive nymphs grow in size and shape by the process of moulting and the successive instars look more alike to adults. There is no resting or transitional phase for transformation into adults e.g. dragonflies, damselflies, grasshoppers, cockroach, crickets, aphids, jassids, bugs etc. The degree of metamorphosis is not the same in all Exopterygota. A few insects like white flies and thrips on their developmental period, pass through a stage called incipient or false pupal stage (comparable to pupa of Holometabola) before emerging as an adults. Such deviation from Hemimetabola is called aberrant Hemimetabola. In few Exopterygota insects, the wings may be lost or may not develop at all, for example, head louse, bed etc. But there are rudiments of wings in the form of wing pad/ buds in these insects and hence these insects are called secondarily wingless insects. In dragonflies the nymphs are aquatic while the adults are aerial and therefore this group is called Hemimetabola.

2) Complete Metamorphosis or Complex or Indirect Metamorphosis:

The group of insects undergoing this type of metamorphosis is also called Holometabola. The insects in this type complete their postembryonic development by assuming much striking morphological changes. In order to attain maturity, this insect pass through four different stages viz. egg, larva, pupa and adult. Since there are many changes in form it is called complex metamorphosis. Young one after hatching from the egg is called larva. The larva differs from its parents in the structure, food, feeding habits, mode of life and habitat. The larvae may have biting type of mouthparts, while adults may have different mouthparts such as siphoning type. Similarly they do not have compound eyes but possesses simple ocelli. Legs are also subjected to compound modifications. Some of the larvae have only three pairs of thoracic legs (beetles & weevils) while in other there may be one or more pairs of abdominal legs in addition to thoracic legs (butterflies & month). In some larvae legs are altogether absent (flies). There are several instars during larval stage. There is altogether absent (flies). There are several instars during larval stage. There are no external signs of presence of wing pads or buds on the larvae. However, these pads are present inside the body cavity in thoracic region. These wing pads develop internally hence; this group of insects is called Endopterygota. Further, for transformation into adults the larva has to pass through a resisting phase or transitional phase called pupa. Feeding and movement ceases and metabolic activities are lowered down during the pupal stage but conspicuous changes in morphological forms in the development of wings and reproductive organs occur in the pupal stage. The adult come out of the pupal covering with development of compound eyes, antennae, thoracic legs, wings reproductive organs and changes in mouth parts. Since, a pupal stage is necessary for the transformation of larva into adult, this type of metamorphosis is called indirect or complete metamorphosis. As Endopterygota insects are included under this type of metamorphosis e.g. Butterflies, moths, beetle, weevils, flies, honeybees, wasps, mosquitoes, etc.

3) Hypermetamorphosis:

This is specialized type of metamorphosis found in higher orders of Endopterygota insects. It is a type of complete metamorphosis in which different larval instars represent two or more markedly different types of larvae. The first instars larva is active and usually campodaeiform and the subsequent larval instars are vermiform or scarabaeiform e.g. blister beetles.

Insect Egg

Egg-stage is the first life stage of an insect. Oviposition (egg deposition) takes place in diverse ways. Eggs may be laid singly or in groups, enclosed in gelatinous masses/scales or may be laid in protective case (egg-pod/ootheca). Mostly, the eggs are laid in a situation where they are afforded some protection or where the young ones on hatching, will have suitable conditions for their development. The number of eggs laid by a female varies (50 to few hundreds) with the insect species.

Majority of insects are oviparous that is young ones hatch from the eggs after they have been laid. However, in few insects (e.g. Aphids) the eggs develop within the uterus of the female and directly living young ones are deposited.

Different Forms of Eggs: Egg of different insects varies greatly in appearance. Most eggs arte spherical, over or elongate, but some are barrel shaped, some are disk-shaped and others are of other shapes. The egg is covered with a shell what varies in thickness, sculpturing and colour. Many eggs are provided with characteristic ridges, spines or other processes and some are brightly coloured.
Structure of typical insect egg:

i. Chorion / Egg shell: It is secreted by the cells of the follicular epithelium of the ovary and is composed of lipo-proteins (arranged in a number of layers) and is devoid of chitin. It is formed by two layers viz. Exochorion (outer) and Endochorion (inner). In some insects, there is a Wax layer coated on the exochorion as outer most layers.

ii. Micropyle: One (or more) small openings through the Chorion, usually at one end of the egg. Spermatozoa enter through the micropyle to fertilize the ovum. Besides, this opening serves as respiratory channel.

iii. Viteline membrane (cell wall): It is a delicate membrane, completely lining the egg shell from inner side which encloses the cytoplasm. Yolk and nucleus. Periplasm is another more delicate lining prevails from inner side of the vetelline membrane.

iv. Cytoplasm: It is the living substance of an egg.

v. Yolk/Deutoplasm: It is the non-living (lifeless) substance of an egg which consists of carbohydrates, proteins and lipids scattered as globules throughout the reticulum of the cytoplasm.

vi. Nucleus: It is highly organized dynamic part of the egg containing chromatin which forms the chromosomes. These are composed of large number of giant molecules of deoxyribonucleic acid (DNA), which are the genes, the bearer of heredity characters.

Types of Insect Larva

The larva is a general term to denote young one or immature stage of insect between egg and pupa having complete and hyper metamorphosis (Holometabolus or Endopterygota insects). The larvae are classified into four groups on the basis of development of appendages.

1. Protopod Larva: In this eggs contain little yolk and larvae hatch out from the eggs, while they are still in early stages of embryonic development. The abdomen is devoid of segmentation and head (cephalic) and thoracic appendages are rudimentary e.g. Larvae of Endoparasitic Hymenoptera.

2. Polypod Larva: This type of larva has well segmented body and possesses three pairs of thoracic legs and 2 to 5 pairs of abdominal prolegs. The reparatory system os peripneustaic type i.e. only prothoracic and abdominal spiracles only are open. These larvae are also termed as “Eruciform” (cylindrical type) e.g. larvae of butterflies and moths. On the basis of number and location of prolegs, these larvae are further classified as:
a) Caterpillar
b) Semilooper and
c) Looper.

a. Caterpillar: It is a type of polypod larva which bears 3 pairs of thoracic legs and 5 pairs of prolegs. The prolegs are present on 3, 4, 5, 6, & 10th abdominal segments e.g. Larva of Lemon butter fly, larva of gram pod borer etc.

b. Semilooper: It is a type of polypod larva which bears 3 pairs of thoracic legs and 3 pairs of prolegs. Prolegs are present on 5, 6, and 10th abdominal segments e.g. Castor Semilooper, cotton Semilooper etc.

c. Looper: It is a type of polypod larva which bears 3 pairs of thoracic legs and two pairs of prolegs on 6th and 10th abdominal segments e.g. Cabbage looper.

3. Oligopod Larva: These larvae have well segmented body and they bear well development cephalic (head) appendages and 3 pairs of thoracic legs. The abdominal appendages (prolegs) are absent. In some larvae a pair of cerci or similar caudal processes may be present. On the basis of structure, the oligopod larvae are further classified into two types viz. a) Campodeiform type b) Scarabaeiform type.

a. Campodeiform Type larva: The larva appear like campodea insect (from order Diplura) and hence the name. These larvae have elongated more or less fusiform (i.e. tapering at both the ends). Some what depressed body which is often well sclerotized bearing long thoracic legs and usually a pair of terminal cerci e.g. Lady Bird beetle, lace wing etc.

b. Scarabaeiform Type Larva: This type of larva is shout, fleshy ‘C’ shaped with shorter thoracic legs and without terminal abdominal processes (cerci). They are less active and sluggish e.g. White grub, rhinoceros beetle etc.

4. Apodous Larva: These larvae do not have either thoracic legs or abdominal prolegs (legless) e.g. House fly, fruit fly, honey bee.
The apodous larvae may be classified into following 3 types on the basis of degree of development of head.

a. Eucephalous Larva: This type of larvae have well sclerotized head capsule with relatively reduced of cephalic appendages e.g. Mosquito, mango stem borer etc.

b. Hemiphaous Larva: This type of larvae appreciably reduced head capsule and its appendages. The head can be withdrawn into the thorax e.g. Honey bees, robber lies, horse flies etc.

c. Acephalous Larva: They have no obvious head capsule and cephalic appendages e.g. Larva of house fly.

Significance of Larva Stage: It helps in increasing size and putting on more weight of insect.

Types of Pupa

Pupa is a non feeding and inactive stage of insect between the larva and adult with complete metamorphosis. The insect pupae are classified into two types on the basis of mode of emergence of adults from the pupal case.

1. Decticous Pupa: In this of pupa, more or less fully formed adult, within the pupal case has relatively powerful sclerotized mandibles by means of which it comes out from the pupa. This type of pupa is always execrated (free) type e.g. Lace wing, Scorpion flies.

2. Adecticous Pupa: In this of pupa, the adult developed within pupal case, often possess reduced and non articulating mandibles which are not utilized for escaping from the pupa. Two main types of adecticous pupae are:

a. Exarate Adecticous Pupa: In this type of pupae the appendages are free of any secondary attachment to the body e.g. Honey bee, wasp, white grub etc.

b. Object Adecticous Pupa: In this type, the appendages are family pressed against its body and are soldered to it e.g. Gram pod borer, lemon butter fly etc.

3. Coarctate Pupa: In this type, the appendages are not visible. The pupa is enclosed in a puparium, formed from the last larval skin. This is clearly adecticous exarate pupa e.g. House fly, fruit fly etc.

Significance of Pupal Stage:

1. Being non feeding stage it avoids or reduces the competition for food.
2. Helps in re-modeling and re-structuring or the body to exploit many habitats.
3. Chances of survival of insects are increased by entering in inactive stages

Collections of Insects

Insects are Required to be Collected for Following Purposes:

1. To know the pest occurrence of the locality.
2. To study the taxonomic characters of the insects.
3. To send the specimens to different places for identification.
4. To keep different insects in museum.
5. To study the bionomics of pests.

I) Equipments Required for Insect Collection:

Equipments:

1. Insect collecting net
2. Insect killing bottle
3. Specimen tubes of various sizes
4. Forceps and hand lens
5. Insect store box
6. Insect rearing cages
7. Insect killing and preserving media
8. Insect setting boards/spreading board
9. Small hair brush
10. Aspirator

i. Hand net: The hand net with a handle nearly 2 ft in length having circular iron ring of 1 ft diameter attached to it. A collecting bag made up of ordinary mosquito netting cloth is attached to the iron ring.

ii. Aspirator: A glass tube is used for collecting small insects which is fitted with a rubber cork. A rubber cork is having two holes in which small tubes are fitted. Out of the small two tubes one is longer and another is shorter, which is used for sucking purpose and enclosed by other end by means of muslin cloth so as not to allow collected insects to escape. The other tube is further fitted with rubber tube which is used for collecting smaller sized insects.

Preservation of Soft Bodied Insects and Permanent Mounting

Preservation of Soft Bodied Insects:

Soft bodied insect like aphids, jassids, thrips, midges, scales bugs and immature life stages of the pests are preserved in 70 75 % ethyl alcohol with little quantity of glycerin in small specimen tubes. The tubes are properly labeled giving details as specified in above Para No. c-i). These insects are also preserved in 5% formalin solution.

Permanent Mounting:

The very small insects are also preserved by mounting on permanent slides. Their various structures and stages are also studied by preserving them by this method. The insects to be preserved are boiled in 10% KOH solution for few minutes then they are to be passed through 20-100% alcohol series for dehydration and then mounted on cavity slides in Canada balsam.