A recessive, sex-linked mutant is described in Eretmapodites quinquevittatus. The mutant, red-eye (re), exhibits complete penetrance and can be determined in the larvae, pupae, and adults of both males and females. Testcross data place re approximately 17 map units from the sex locus (m) on linkage group I. Sex determination in Er. quinquevittatus is similar to that of other Culicine mosquitoes (M/m = male).