Females in all stages apterous; metamorphosis semi-complete; naked or covered; active or stationary; rostrum usually present in all stages, sometimes absent in adult; feet sometimes absent after larval stage; tarsi where present monomerous; feet, where present, ending in a single claw; eyes sometimes absent.
Male pupæ apterous; naked or covered. Adult males with two wings and two halteres; metamorphosis complete; rostrum present in larva and pupa, always absent in adult; tarsi monomerous; feet ending in a single claw; abdomen terminating in a spike which forms the sheath of the penis; eyes present in adult; ocelli often large, sometimes exceeding three in number.
The above characters sufficiently distinguish this family from the rest of the Homoptera. Probably the first marks for identification of a specimen might be the monomerous tarsus and the single claw. The latter is always to be made out, at least in the earlier stages of the female and in the adult male.
GROUPS.
Larvæ active, naked; adult females and pupæ stationary, covered with separate shields or puparia, composed partly of secretion, partly of the earlier discarded pellicles; females apodous after larval stage; abdomen of females not exhibiting a median cleft or dorsal lobes
Larvæ active, naked; adult females and pupæ active or stationary, naked or covered with secretion; adults sometimes apodous; abdomen of females exhibiting a median cleft and two dorsal lobes
Larvæ active, naked, exhibiting at the abdominal extremity two protruding anal tubercles. Adult females exhibiting abdominal cleft and dorsal lobes; naked or covered with secretion