Abdominal structures in insects
i) Pregenital abdominal appendages in wingless insects:
1) Styli : (Stylus : Singular) Varying number of paired tube like outgrowths are found on the ventral side of the abdomen of silverfish. These are reduced abdominal legs which help in locomotion.
2) Collophore or ventral tube or glue peg: It is located on the ventral side of the first abdominal segment of spring tail. It is cylindrical. It is protruded out by the hydrostatic pressure of haemolymph. It might serve as an organ of adhesion. It aids in water absorption from the substratum and also in respiration. 3). Retinaculum or tenaculum or catch: It is present on the ventral side of the third abdominal segment. It is useful to hold the springing organ when not in use.
4) Furcula or Furca: This is a 'Y' shaped organ. It is present on the venter of fourth abdominal segment. When it is released from the catch, it exerts a force against the substratum and the insect is propelled in the air.
ii) Abdominal appendages in immature insects:
2) Anal papillae: A group of four papillae surrounds the anus in mosquito larvae. These papillae are concerned with salt regulation.
3) Dolichasters: These structures are found on the abdomen of antlion grub. Each dolichaster is a segmental protuberance fringed with setae.
4) Proloegs: These are present in the larvae of moth, butterfly and sawfly. Two to five pairs are normally present. They are unsegmented, thick and fleshy. The tip of the proleg is called planta upon which are borne heavily sclerotised hooks called crochets. They aid in crawling and clinging to surface.
iii) Abdominal appendages in winged adults :
2) Caudal breathing tube: It consists of two grooved filaments closely applied to each other forming a hollow tube at the apex of abdomen. e.g. water scorpion.
3) Cerci : (Cercus - Singular) They are the most conspicuous appendages associated normally with the eleventh abdominal segment. They are sensory in function. They exhibit wide diversity and form.
Long and unsegmented :- e.g. Cricket
Short and many segmented :- e.g. Cockroach
Short and unsegmented :- e.g. Grasshopper
Sclerotised and forceps like : e.g. Earwig. Cerci are useful in defense, prey capture, unfolding wings and courtship.
5) Pygostyles: A pair of unsegmented cerci like structures are found in the last abdominal segment of scoliid wasp.
6) Anal styli: A pair of short unsegmented structure found at the end of the abdomen of male cockroach. They are used to hold the female during copulation.
7) Ovipositor: The egg laying organ found in female insect is called ovipositor. It is suited to lay eggs in precise microhabitats. It exhibits wide diversity and form. Short and horny : e.g. Short horned grasshopper
Needle like : e.g. Cricket
Ovipositor modified into sting : e.g. Worker honey bee.
Last modified: Friday, 18 November 2011, 2:20 PM