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.