Insect Body Regions

The principal body regions of insects are the head, thorax and abdomen (Fig. 2.3 ). Each region, or functional unit, is called a tagma (plural, tagmata ), and the process of the individual segments functioning as a unit is called tagmosis . The presence of these three body regions is not always apparent, however. The head may be small or hidden from view when examined from above, or the front wings may cover both the thorax and abdomen, giving the impression that there is only a single large segment. Alternatively, when viewed from below it is evident that insects consist of quite a large number of segments, some of which are fused. Even after fusion, it usually is possible to recognize three thoracic segments and about 11 abdominal segments. The six segments that fused to form the head are mostly unrecognizable. Legs, wings, and antennae are the appendages that are most evident on the tagmata, but often mouthparts and cerci can be seen.