[Presence in Camargue of two sympatric, sexually isolated forms of Aedes (Ochlerotatus) detritus (Haliday, 1833) [Diptera-Culicidae] (author's transl)].

The study of allozymic variations at four enzymatic loci (Est-2, alpha-Gpd, Got-1 and Got-2) in populations of Aedes detritus (Hal.) from 27 localities in Southern France has shown that this species is composed of two kinds of sympatric populations which do not interbreed in nature. Single specimens of Aedes detritus can be attributed to one or other type of population (sibling species) by the genotype at the alpha-Gpd or Got-2 loci (type A populations are homozygous for Got-2R allele and the frequency of the alpha-GpdC allele is higher than 98%; type B populations are homozygous for Got-2L allele and the frequency of the alpha-GpdB allele is higher than 98%). Moreover, allelic frequencies at the Est-2 and Got-1 loci are different in both types of populations. The fact that both kinds of populations coexist in the same pond shows that the isolating mechanism is not an adaptation to the larval environment, but rather involves mechanisms pecular to adults (precopulatory mechanism or interpopulation sterility).