In this monophyletic group, the head is held deflexed under the body. The rostrum arises from the venter of the head between the front coxae (near or on the prosternum), and is held with its entire length in contact with the body when not in use. The wings are folded into a roof-like arrangement over the abdomen at rest. The forewing is of an even thickness throughout (either thickened or membranous); occasionally the wings are short (brachypterous) or absent (apterous). The hind wing lacks a vannus and vannal fold. Each tarsus has only 1 or 2 tarsomeres. The antennal tip is formed by a living, fleshy flagellum. Tympannal organs are absent. All Sternorrhyncha are plant feeders. Evolutionary trends within the Sternorrhyncha are: towards smaller size, a reduction in morphological complexity (including wing venation), increased biological complexity, nymphal regression and sessility, and production of protective devices (scale covers, tests, pits and galls).