CHROMOSOME CHANGES AND INSECTICIDE RESISTANCE IN ANOPHELES QUADRIMACULATUS.

Certain insecticide-resistant strains of anopheline mosquitos found in the field or developed in the laboratory are known to contain a high proportion of heterozygotes for chromosomal inversions, but up till now it has not been clear how this could be causally related to resistance. In the present investigation, 2 resistant strains and 2 susceptible strains of Anopheles quadrimaculatus, and the hybrids between them, were examined for the frequency of inversions. It was found that neither the resistant nor the susceptible strains were characterized by inversion buckles. Moreover, no new inversions appeared in the hybrids between them. It was therefore concluded that where heterozygosity for inversions has been observed in anophelines, it is a characteristic of hybrids due to parental differences resulting from geographic separation, and has no relation to specific insecticide resistance.