Descriptive and linkage studies have been conducted for a homeotic mutant, proboscipedia (prb) in Aedes aegypti (L.). The mutant was isolated from a strain of palp-extended (pe), a recessive, sex-linked and sex-limited mutation, collected in Dar es Salaam, Tanzania. In addition to descriptions of various labellar and maxillary palp modifications produced by the homeotic condition, environmental effects on penetrance were also considered; cooler rearing temperatures producing an increase in the penetrance. Linkage studies, due to female sterility, are based on F2 data show the mutant prb to be a genetically controlled recessive located between red-eye (re) and sex (m) on linkage group I. Homeotic mutants provide excellent means of studying imaginal disc development in homometabolous insects but due to female sterility of the prb mutation its use as a genetic marker is severely limited.