Class Insecta-General characters-Bsc Complementary Zoology Notes

Insecta

Insects are air breathing mostly terres-trial and rarely aquatic arthropods.

 2.Body is divided into three distinct re-gions, head, thorax and abdomen

 3.Head consists of six fused segments and bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chew-ing, biting, piercing, sucking, siphoning or sponging type.

 4.Thorax comprises three free segments each bearing a pair of legs and two pairs of wings borne on the second and third segments.

5.Abdomen comprises 7-1 I segments devoid of appendages.

6. Liver is absent but salivary glands are usually present.

7. Heart is elongated, tubular and isdivided into eight chambers situated in the abdomen.

8.Respiration by branched tracheae.

9. Excretion by malpig,hian tubules.

10. Sexes are separate

 II. Development is sometimes direct, Tor =ally complicated by metamorphosis.