The forewings have at least a single longitudinal nervure - often two - reaching from base to tip of the wing.
Forewings similar in shape and texture to hind-wings, which do not fold.
The order must therefore be ancient, and as no evidence is forthcoming as to the mode of reduction of the hind-wings, nor as to the stages by which the suctorial mouth-organs became specialized, it is difficult to trace the exact relationship of the group, but the presence of cerci and a degree of correspondence in the nervuration of the forewings suggest the Mecaptera as possible allies.
The Cimicidae have the feet three-segmented and the forewings greatly reduced; most of the species are parasites on birds and bats, but one - Cimex lectularius (figs.
Jaws under Hexapoda); in the presence of a large number of excretory (Malpighian) tubes; in the firm texture of the forewings; in the presence of appendages (cerci) on the tenth abdominal segment; and in the absence of a metamorphosis, the young insect after hatching closely resembling the parent.