The labiohypopharynx of 62 species of fourth stage culicid larvae representing 3 genera of the Dixinae, 2 of the Chaoborinae and all but one (Ficalbia) of the 34 genera recognized by Knight and Stone (1977) have been studied with the light and scanning electron microscopes. The structure of the labiohypopharynx is described and illustrated for at least one species of each genus examined. Phylogenetic relationships are discussed in regard to larval morphology and feeding behavior.