A) Insect Antenna
General Structure
- Most insects have a single pair of antennae.
- Each antenna consists of three main parts:
- Scape – Basal segment, articulates with the head.
- Pedicel – Second segment, contains Johnston’s organ (sound & vibration reception).
- Flagellum (Flagellum) – Remaining segments (flagellomeres), variable in number.
Functions
- Smell (olfaction) – primary function.
- Taste – detects food or mates.
- Hearing – in male mosquitoes (Johnston’s organ).
- Sound production – in mole crickets (via pedicel).
- Touch, humidity, and temperature perception in some species.
Types of Insect Antennae
|
S.No. |
Type |
Features |
Example |
|
1 |
Setaceous |
Segments taper from base to apex; slender and pointed |
Cockroach, Leafhoppers |
|
2 |
Filiform |
Thread-like; all segments uniform in size |
Grasshopper |
|
3 |
Moniliform |
Bead-like; segments globular with constrictions between |
Termites |
|
4 |
Serrate |
Each segment has saw-like projections |
Pulse beetle |
|
5 |
Pectinate |
Each segment bears long, comb-like projection on one side |
Sawfly |
|
6 |
Bipectinate |
Comb-like projections on both sides |
Silkworm moth |
|
7 |
Plumose |
Whorls of hairs on each segment; feathery appearance |
Male mosquito |
|
8 |
Whorled |
Bristles arise in whorls on each segment |
Mango mealy bug |
|
9 |
Clavate |
Terminal segments form a club-shaped structure |
Butterflies, Blister beetles |
|
10 |
Capitate |
Terminal segment forms a large knob or cap |
Khapra beetle |
|
11 |
Geniculate |
Elbowed; first segment long, second small forming an angle |
Bees, Ants, Weevils |
|
12 |
Aristate |
Short, pouch-like with a bristle (arista) on last segment |
Housefly |
B) Types of Insect Mouthparts
Basic Components
- Labrum – Upper lip
- Mandibles (1 pair) – For cutting and grinding food
- Maxillae (1 pair) – Manipulating food; consist of cardo, stipes, galea, lacinia, palpi
- Labium – Lower lip (submentum, mentum, prementum, palpi)
- Hypopharynx – Tongue-like; forms salivarium
- Epipharynx – Contains taste sensilla
Types of Mouthparts
|
S.No. |
Type |
Structure & Adaptation |
Example |
|
1 |
Biting & Chewing |
Typical type; mandibles well-developed for chewing |
Grasshoppers, Locusts, Termites, Beetles |
|
2 |
Piercing & Sucking (Bug type) |
4 stylets (2 mandibles + 2 maxillae); food canal formed by maxillae |
Bugs, Aphids, Jassids, Whiteflies |
|
3 |
Piercing & Sucking (Mosquito type) |
6 stylets (2 mandibles, 2 maxillae, labrum-epipharynx, hypopharynx); food canal formed by labrum-epipharynx |
Mosquitoes |
|
4 |
Sponging |
Mandibles absent; labium forms proboscis with labellum and pseudotracheae |
Housefly |
|
5 |
Siphoning |
Maxillary galeae form a coiled proboscis; labrum & mandibles rudimentary |
Butterflies, Moths |
|
6 |
Chewing & Lapping |
Mandibles chew; labium forms lapping proboscis |
Honeybee, Wasp |
|
7 |
Rasping & Sucking |
3 stylets (2 maxillae + 1 left mandible); asymmetrical mouthparts |
Thrips |
C) Insect Legs
General Structure
Each thoracic segment bears one pair of legs (total 3 pairs).
A typical insect leg consists of:
- Coxa – basal segment
- Trochanter – small connecting segment
- Femur – large, muscular segment
- Tibia – long, slender segment
- Tarsus (Tarsi) – usually 1–5 subsegments
- Pretarsus – bears claws, pads, or arolia
Leg Modifications
|
S.No. |
Type of Leg |
Function |
Example |
|
1 |
Ambulatorial |
Walking |
Cockroach |
|
2 |
Saltatorial |
Jumping |
Grasshopper (hind legs) |
|
3 |
Cursorial |
Running |
Ants, Wasps |
|
4 |
Scansorial |
Clinging or grasping hair |
Head louse |
|
5 |
Stridulatory |
Sound production |
Crickets |
|
6 |
Fossorial |
Digging |
Mole cricket (forelegs) |
|
7 |
Natatorial |
Swimming |
Water beetle (Dytiscus) |
|
8 |
Raptorial |
Grasping prey |
Mantis (forelegs) |
|
9 |
Foragial (Pollen basket) |
Pollen collection |
Worker bee (hind legs) |
Quick Revision Pointers
- Antenna parts: Scape – Pedicel – Flagellum
- Johnston’s organ: in Pedicel
- Sound-producing antenna: Mole cricket
- Piercing-sucking mouthparts: Bugs, Mosquito
- Siphoning mouthparts: Butterfly
- Lapping mouthparts: Honeybee
- Jumping legs: Grasshopper
- Digging legs: Mole cricket
- Swimming legs: Dytiscus
- Pollen basket: Worker honeybee
Insect Physiology (Introduction)
- Definition: Study of the functional and biochemical processes in insects.
- Father of Insect Physiology: Sir Vincent Brian Wigglesworth
- Book: Principles of Insect Physiology
- Model organism studied: Rhodnius prolixus (Kissing bug)
