Means of locomotion of 48 species of larval mosquitoes was observed using cinematography in Panama, Honduras and neotropical Mexico. General observation led to a classification of movement into path, frequency, position and mechanism. Examination of high speed film sequences (64 frames per second) revealed that all species use the same basic mechanism of flexing, which consists of a power and a recovery phase. The entire flexing cycle is a modification of undulatory propulsion commonly observed in other animals (e.g., snakes, ceratopogonid larvae). Variations on the basic patterns of mosquito larval flexing mainly concern the speed of the power stroke and the degree of sinusoid curvature prior to the power stroke. Four basic patterns of larval flexing were discerned: irregular, sinuous, semisymmetric and anopheline. Some taxonomic groups appear to use one pattern of flexing exclusively or with few exceptions. Examples include Culex (Melanoconion) with sporadic irregular flexing, Cx. (Culex) with sustained irregular flexing, Haemagogus with slow sinuous flexing and Anopheles with anopheline flexing. Other groups (e.g., Aedes (Howardina), Cx. (Carrollia), Deinocerites, and Wyeomyia (Wyeomyia] use a number of patterns of flexing. Observation of flexing and other aspects of larval movement can be an important addition to geographical, habitat and morphological considerations in field identifications.