Agricultural Entomology Basic Study Point
Agricultural Entomology Basic Study Material
1.Presence of special types of reproduction other than oviparity and viviparity.
| Reproduction Type | Examples |
| Polyembryony | Development of many individuals from a single egg. e.g. Parasitic wasps. |
| Parthenogenesis | Reproduction without male or without fertilization, e.g. Aphids |
| Paedogenesis | Reproduction by immature stages. e.g. Certain flies |
2.Defense mechanisms:- By using the following defense mechanisms, insects escape from the enemies to increase their survival rate.
| Defense Mechanisms In Insect | |
| Features | Examples |
| Behavioural Mechanisms | |
| (Thanatosis) Insects pretends as if dead | Some beetles. |
| Structural Mechanisms | |
| hardened forewings of beetles known as elytra protect the beetles from predation of birds. | Beetles |
| Colourational Mechanisms | |
| resence of protective colours | Stick insects |
| Chemical Mechanisms | |
| Presence of defensive chemicals. | Bees producing venom |
3.Structure & Functions Of Insect Cuticle and Moulting
Insect Body wall:- Insect body wall is called as Integument or Exoskeleton. It is ectodermal in origin.
Structure of Insect Body wall:-
Insect Body wall consists of two layer
- Epidermis:- Inner cellular layer. Main function Cuticle secretion
- Cuticle:- An outer non cellular part.
Cuticle Consist Three Parts:-
- Endocuticle:- This layer is made up of Chitin and arthropodin. This layer is colourless, soft and flexible.
- Exocuticle:- Composition of Chitin and sclerotin. This layer is dark in colour and rigid.
- Epicuticle:- This layer is differentiated into the following layers.
- Inner epicuticle:- It contains wax filaments
- Outer epicuticle:- It makes the contact with cuticulin
- Cuticulin:- Non chitinous polymerised lipoprotein layer.
- Wax layer:- It contains closely packed wax molecules which prevents desiccation.
- Cement layer:- Outer most layer formed by lipid and tanned protein. It protects wax layer.
Composition of cuticle:-
- Chitin:- It is the main constituent of cuticle, which is Nitrogenous polysacharide and polymer of N-acetylglucosamine. It is water insoluble but soluble in dilute acids, alkalies and organic solvents.
- Arthropodin:- An untanned cuticular protein, which is water soluble.
- Sclerotin:- Tanned cuticular protein, which is water insoluble.
- Resilin:- An elastic cuticular protein responsible for the flexibility of sclerites, e.g., wing articulatory sclerites.
Endoskeleton:- Cuticular in growth of body wall providing space for muscle attachment is known as endoskeleton. There are two types
| Endoskeleton | Features |
| Apodeme | Hollow invagination of body wall. |
| Apophysis | Solid invagination of body wall. |
4.Cuticular Appendages
| Multicellular | |
| Types | Examples |
| Movable | Spur |
| Immovable | Spine |
| Unicellular | |
| Clothing hairs, Plunose hairs |
Honey bee
|
| Bristles | Flies |
| Scales attened out growth of body wall | Moths and butter flies |
| Glandular seta | Caterpillar |
5.Different Types Of Insect Glands
| Glands | Examples |
| Wax gland | Honey bee and mealy bug |
| Lac gland | Lac insects |
| Androconia or scent scale | Moth |
| Poison gland | Slug caterpillar |
Body Segmentation:- Insect body is differentiated into three distinct regions called head, thorax and abdomen (grouping of body segments into distinct regions is known as tagmosis and the body regions are called as tagmata).
1.Head:- Head is attached or articulated to the thorax through neck or Cervix
Types of insect heads:- Based on the inclination of long axis of the head and orientation of mouth parts there are three types of insect heads.
- Hypognathous:- (Hypo means below and Gnathous means jaw). This type is also called orthopteroid type. The long axis of the head is vertical. It is at right angles to the long axis of the body. Mouth parts are ventrally placed and project downwards.
- Prognathous:- (Pro means infront & Gnathous means jaw). This type is also called coleopteroid type. The long axis of the head is horizontal. It is in line with the long axis of the body. Mouth parts are directed foreward. Example:- groung beetles.
- Opisthognathous:- (Opistho means behind & Gnathous means jaw. This type is also called hemipteroid type or opisthorhychous. Head is deflexed. Mouth parts are directed backwards and held in between the fore legs. Eg: Stink bug.
2. Thorax:- Second and middle tagma which is three segmented, namely prothorax, mesothorax and metathorax. Meso and metathorax with wing are called as Pterothorax. Thorax is made up of three scleritic plates namely, dorsal body plate (Tergum or Nota, ventral body plate (Sterna) and lateral plate (Pleura)
Functions of thorax:- Mainly concerned with locomotion.
3. Abdomen:- Third and posterior tagma. This tagma is made up of 9-11 Uromeres (segments). Each abdominal segment is made up of only two sclerite namely dorsal body plate (tergum) and ventral body plate (sternum)
Function:- Concerned with reproduction and metabolism.
Legs and their modification:- The fore-legs are located on the prothorax, the mid-legs on the mesothorax, and the hind legs on the metathorax. Each leg has six major components, listed here from proximal to distal.
6.Six major components of Legs
| No. | Components of Legs |
| 1 | Coxa (plural coxae) |
| 2 | Trochanter |
| 3 | Femur (plural femora) |
| 4 | Tibia (plural tibiae) |
| 5 | Tarsus (plural tarsi) |
| 6 | Pretarsus |
Agricultural Entomology Basic Study Table
7.The Term Pretarsus Including
| Definition | Term |
| A pair of claws is called? | Ungues |
| A lobe or adhesive pad between the claws is called? | Arolium |
| A large bristle (or lobe) between the claws is called? | Empodium |
| A pair of adhesive pads is called? | Pulvilli |
8.Without metamorphosis Insect
| Orders | Examples |
| Collembola | Silverfish |
| Collembola | Springtail |
| Mallophaga | Chewing Lice |
| Anoplura | Sucking Lice |
9.Incomplete or Gradual Metamorphosis
| Orders | Examples |
| Orthoptera | Grasshoppers |
| Isoptera | Termites |
| Psocoptera (Corrodentia) | Booklice |
| Thysanoptera | Thrips |
| Hemiptera | True Bugs |
| Homoptera | Aphids |
| Dermaptera | Earwigs |
10.Complete Metamorphosis
| Orders | Examples |
| Neuroptera | Lacewing |
| Coleoptera | Beetles |
| Mecoptera | Scorpionfly |
| Trichoptera | Coddisfly |
| Lepidoptera | Moths, Butterflies |
| Diptera | Flies |
| Siphonaptera | Fleas |
| Hymenoptera | Wasps, Bees |
11.Different Types of eggs
| Singly laid | |
| Features | Examples |
| Sculptured Egg | |
| Chorion with reticulate markings and ridges | Castor butterfly |
| Elongate Egg | |
| Eggs are cigar shaped | Sorghum shoot fly. |
| Rounded Egg | |
| Eggs are either spherical or globular | Citrus butterfly. |
| Nit Egg | |
| Egg of head louse is called nit | Head louse |
| Egg with float | |
| Egg is boat shaped with a conspicuous float on either side | Anopheles mosquito. |
| Laid in groups | |
| Pedicellate Eggs | |
| Eggs are laid in silken stalks of about 1.25 mm length in on groups plants | Green lace wing fly |
| Barrel shaped Eggs | |
| Eggs are barrel shaped. | Stink bug. |
| Ootheca Egg | |
| Eggs are deposited by cockroach in a brown bean like chitinous capsule. | Cockroach |
| Egg Pod | |
| Grass hoppers secrete a frothy material that encases an egg mass which is deposited in the ground | Grass hoppers |
| Egg Case | |
| Mantids deposit their eggs on twigs in a foamy secretion called spumaline. | Mantids |
| Egg Mass | |
| Moths lay eggs in groups in a mass of its body hairs | Rice stem borer. Female silk worm moth |
| Egg raft | |
| Eggs are laid in a compact mass consisting of 200 – 300 eggs are called egg raft in water. | Culex mosquitoes |
Larvae:- There are three main types of insects larvae namely oligopod, polypod and apodous
Oligopod have some subtypes:- Campodeiform Larvae & Scarabaeiform Larvae
12.Different Types of Larvae
| Larvae | |
| Oligopod | |
| There are Two subtypes | |
| Features | Examples |
| Campodeiform Subtype | |
| Larvae are generally predators and are very active | Grub of ant lion or Grub of lady bird beetle. |
| Scarabaeiform Subtype | |
| Body is ‘C’ shaped, stout and subcylindrical. | Grub of rhinocerous beetle |
| Polypod or Eruciform | |
| The body consists of an elongate trunk with large sclerotised head capsule | Caterpillar (larvae of moths and butterflies) |
| Hairy Caterpillar | |
| The body hairs may be dense, sparse or arranged in tuftslled nit | Red hairy caterpillar. |
| Slug Caterpillar | |
| larva is thick, short, stout and fleshy larva is also called platyform larva. | Platyform larva. |
| Semilooper | |
| Either three or four pairs of prologs are present. | Castor semilooper. |
| Looper | |
| They are also called measuring worm or earth measurer or inch worm. | Daincha looper |
| Apodous | |
| There are three subtypes | |
| Eucephalous Subtype | |
| Mandibles act transversely | Wriggler (larva of mosquito) and grub of red palm weevil. |
| Hemicephalous Subtype | |
| Mandibles act vertically | Larva of horse fly and robber fly. |
| Acephalous Subtype | |
| They are also called vermiform larvae. | maggot (larva of housefly) |
Agricultural Entomology Basic Study Table
