They are easily identified by their 3 pairs of legs, and 3 main body parts, the head, thorax, and abdomen. Insects are protected by a hard exoskeleton made of chitin. Most insects have large compound eyes and antennae. The most primitive insect groups are wingless, although some advanced insect groups, like the fleas, have subsequently lost their wings. Most insects reproduce sexually, although some insects, like aphids, can reproduce asexually.
All insects lay eggs.
In more primitive insects the newly hatched offspring look very much like miniatures of their parents. Diversity of Insects Insects are the most diverse group of animals. Insects are most diverse in the tropics where the combination of high plant diversity and warm climates provides a great number of microhabitats. In the U.S. and Canada there are 91,000 known species and probably about 67,000 undescribed species. The insects are divided into 32 orders according to morphological and genetic relationships.