What signs in the external structure of insects makes it possible to classify it as an insect?

Insects, as well as crustaceans and arachnids, belong to the Arthropod type. Therefore, their body consists of segments and is covered with a chitinous cover.

And the differences in the class of insects are as follows:
the body consists of the head, chest and abdomen;
the chest is formed by 3 segments;
on each segment of the chest – a pair of legs, that is, there are 6 of them;
there are 2 pairs of wings;
compound faceted eyes;
a pair of antennae – sense of smell; a pair of palps – touch;
each segment of the abdomen has a pair of airways called spiracles.