A first mutation in a laboratory strain of the floodwater mosquito Aedes vexans is described. Partly colored larva (pcl) is inherited monofactorially as a recessive autosomal lethal, causing only dark coloration of the head capsule, the saddle on abdominal segment X and the respiratory siphon during the 4th larval stage. All mutants die in the 4th larval (49%) or pupal stage. The sex-linked mutant white eye (w) was used in crosses to show autosomal inheritance.