The thorax is the midsection (tagma) of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods.
It is formed by the prothorax, mesothorax and metathorax and comprises the scutellum; the cervix, a membrane that separates the head from the thorax; and the pleuron, a lateral sclerite of the thorax.
In dragonflies and damselflies the mesothorax and metathorax are fused together to form the synthorax.
In some insect pupae, like the mosquitoes', the head and thorax can be fused in a cephalothorax.
Members of sub order Apocrita (wasps, ants and bees) in the order Hymenoptera have the first segment of the abdomen fused with the thorax, which is called the propodeum.
The thorax in various types of insect