Insect integument - Entomology

General structure and function of Insect integument - Agricultural entomology

1. INSECT INTEGUMENT Jyothis P Joseph MSc. Agri. Entomology Kerala Agriculture University

2. Insect body wall – Integument/Exoskeleton External covering – ectodermal in origin Rigid, flexible, lighter, stronger and variously modified Integument....

3. Consists of 3 layers : Structure Integument Cuticle Epidermis Basement membrane

4. Outer non-cellular layer – has 2 sub-layers Epicuticle : outer most layer – very thin – devoid of chitin Differentiated into 5 layers: Cement layer – outer most layer – made of lipid and tanned protein – protects wax layer. Wax layer – contains closely packed wax molecules – prevents desiccation Cuticulin – Non-chitinous polymerised lipoprotein layer – barrier to ions Outer Epicuticle Inner Epicuticle Cuticle....

5. Procuticle – divided into 2 – Outer exocuticle & Inner Endocuticle . Exocuticle : Outer layer – much thicker – composed of Chitin & Sclerotin – Dark and rigid Endocuticle – Inner layer – thickest layer – made of chitin & Arthropodin – Colourless, soft and flexible. Epidermis: Inner unicellular layer resting on basement membrane – Functions: Cuticle secretion Digestion and absorption of old cuticle Wound repairing Gives surface look

6. Composition.... Chitin: Main constituent of cuticle Nitrogenous polysaccharide and polymer of N- acetylglucosamine . Arthropodin : Untanned cuticular protein Sclerotin : Tanned cuticular protein Resilin : Elastic cuticular protein – for flexibility of sclerites

7. Cuticular in growth of body wall – provide space for muscle attachment. 2 types: Apodeme – hollow invagination of body wall Apophysis – Solid invagination of body wall Endoskeleton...

8. 2 types: Cuticular Appendages... Non- cellular Cellular Multi-cellular Uni -cellular

9. Non-cellular : have no epidermal association but rigidly attached. Eg: minute hairs & thorns Cellular: have epidermal association

10. Unicellular.... Clothing hair or plumose hair : Honey bees Bristles : Flies Scales – Flattened outgrowth of body wall: Butterflies & Moths Glandular seta : Caterpillar Sensory seta: Seta – hair like outgrowth Setae forming cell – Trichogen Socket forming cell – Tormogen Study of arrangement of seta - Chaetotaxy

11. Clothing hair Bristles Glandular Seta

12. Multi-cellular... Spur – movable structure : Eg: Delphacidae Spine – Immovable structure:

13. Wax glands : Honey bees & mealy bugs Lac gland : lac insect Moulting gland secreting moulting fluid Androconia or scent gland : moth Poison Gland : Slug caterpillar Glands....

14. Acts as external armour and strengthens external organs Protects the organs against physical aberration, injurious chemicals, parasites, predators and pathogens Internally protects vital organs Provides space for muscle attachment Gives shape to the body Prevents water loss Cuticular pigments give color Helps in sensing the environment Functions...

15. Thank You