A number of interesting larval mutants have been found in natural populations of Culex quinquefasciatus. These mutants golden yellow (go), greyish brown (gb), brown (br) and green (g) are all autosomal recessives with full penetrance and high viability in both the sexes,. Crosses were made among these mutants to test for allelism. The mutant green was found to be dominant over brown, greyish brown and golden yellow. Brown was dominant over golden yellow and greyish brown. These color mutants appear to belong to an allelic, with intermediate expression in the heterozygotes condition. The fact that all the 4 mutants apparently belong to an allelic series is perhaps expected but these experimental results provide, for the first time, direct support for this assumption.