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The “tergal hypothesis” suggests that wings originated on the tergum — the top of the insect body wall — perhaps as gliding membranes.

Ter′gite, the tergum or back of one of the somites or segments of an arthropod, &c.—adj.

Somite of a Lobster, separated and viewed from in front. t, tergum; s, sternum; pl, pleuron.

A dorsal and a ventral plate are often distinguished, known respectively as the tergum and the sternum, and the tergum may overhang the insertion of the limb on each side as a free plate called the pleuron.

In the Achorutidae the head is forwardly directed, the tergum of the prothorax conspicuous, and the spring small or vestigial.