Elytron(redirected from elytroid)
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one of the anterior wings that in most insects cover the posterior wings when the latter are folded along the dorsal wall of the body. Beetles have thickened elytra with practically no evidence of venation. The elytra of the Dictyoptera and Orthoptera are leathery and have noticeable or pronounced venation. Some insects, such as earwigs, have veinless elytra. In bedbugs, only the base of each elytron is thickened; the tip is membranous.
Elytra that are particularly thick no longer function as active organs of flight, becoming merely carrying surfaces (as in the June beetle), or play no role in flight at all (for example, the Cetonia). Many beetles in desert regions have greatly reduced posterior wings, and their elytra, as a rule, have fused to form a solid cover over the abdomen. The cavity under the elytra is exposed to the external atmosphere by a small opening at the top of the abdomen. Spiracles open into the cavity; the air in the cavity is heavily saturated with water vapor to minimize water loss during respiration. In many water beetles, for example the Dytiscidae, the cavity stores air, which the beetle can breathe as it swims through the water.
M. S. GILIAROV