General Entomology

1. Entomology = study of insects (Greek: Entomon = insect, Logos = study).
2. Father of Entomology – William Kirby.
3. Father of Indian Entomology – Dr. T.B. Fletcher.
4. Father of Modern Entomology – Aristotle.
5. Insect body divided into head, thorax, and abdomen.
6. Number of legs in insects – 6 (3 pairs).
7. Insects belong to phylum Arthropoda, class Insecta.
8. Insect cuticle made of chitin (a polysaccharide).
9. Chitin secreted by epidermal cells.
10. Sclerotization (hardening) due to quinone tanning of cuticle.
11. Molting (Ecdysis) is shedding of old cuticle during growth.
12. Ecdysone hormone induces molting.
13. Juvenile hormone (JH) maintains larval stage.
14. Head bears antennae, eyes, and mouthparts.
15. Thorax has 3 segments – prothorax, mesothorax, metathorax.
16. Wings are present on meso- and metathorax.
17. Antennae used for smell, touch, and orientation.
18. Insect eyes – simple (ocelli) and compound eyes.
19. Number of ommatidia in compound eye – 3000–30,000.
20. Types of mouthparts – biting-chewing, piercing-sucking, siphoning, sponging, chewing-lapping.
21. Biting-chewing type – Grasshopper, termite, beetle.
22. Piercing-sucking type – Mosquito, bug, aphid.
23. Siphoning type – Butterfly, moth.
24. Sponging type – Housefly.
25. Chewing-lapping type – Honeybee.

Internal Systems

1. Digestive system – foregut, midgut, hindgut.
2. Excretory organs – Malpighian tubules.
3. Circulatory system – open type with hemolymph.
4. Insect heart is tubular and dorsal.
5. Respiration through tracheal system with spiracles.
6. Spiracles – 10 pairs (2 thoracic + 8 abdominal).
7. Respiratory pigment – absent (no hemoglobin).
8. Nervous system – brain + ventral nerve cord.
9. Endocrine glands – corpora allata, corpora cardiaca, prothoracic gland.
10. Reproduction – mostly oviparous.
11. Sex determination – XX (female), XY (male).
12. Eggs laid through ovipositor.
13. Parthenogenesis – development from unfertilized eggs (aphids).
14. Viviparity – giving birth to larvae (tsetse fly).
15. Polyembryony – many embryos from one egg (Braconids, Trichogramma).

Insect Development

1. Metamorphosis – change from egg to adult.
2. Types:

• • Ametabolous – no metamorphosis (silverfish)
  • Hemimetabolous – incomplete (grasshopper, bug)
  • Holometabolous – complete (butterfly, beetle)

1. Instar – stage between two molts.
2. Pupa – inactive, non-feeding stage in holometabolous insects.
3. Diapause – developmental arrest under unfavorable conditions.
4. Quiescence – temporary dormancy due to environment.
5. Polymorphism – occurrence of multiple forms (ant, termite, bee).
6. Dimorphism – male and female forms differ.
7. Seasonal polymorphism – different forms in different seasons (aphid).
8. Color polymorphism – same species showing color variation.

Economic Entomology

1. Insects of agricultural importance – pests, pollinators, parasitoids, predators.
2. Pest – any organism causing economic loss to crops.
3. Economic threshold level (ETL) – pest density at which control needed.
4. Economic injury level (EIL) – pest density where loss equals control cost.
5. IPM (Integrated Pest Management) – eco-friendly pest control strategy.
6. ETL = EIL / Damage potential × Effectiveness × Cost ratio.
7. Defoliators – feed on leaves (Spodoptera, Helicoverpa).
8. Borers – feed inside plant tissues (stem borer, shoot borer).
9. Sucking pests – suck sap (aphid, jassid, whitefly).
10. Root feeders – termites, white grubs.
11. Fruit borers – Helicoverpa armigera (tomato, cotton, chickpea).
12. Stem borer of rice – Scirpophaga incertulas (yellow stem borer).
13. Sugarcane top borer – Scirpophaga excerptalis.
14. Cotton bollworm – Helicoverpa armigera.
15. Jassid of cotton – Amrasca biguttula biguttula.
16. Whitefly vector of cotton leaf curl virus – Bemisia tabaci.
17. Aphid vector of potato virus – Myzus persicae.
18. Brown planthopper (BPH) – Nilaparvata lugens (rice).
19. Green leafhopper (GLH) – Nephotettix virescens (rice tungro virus).
20. Termites – feed on roots and stems underground.