Resistance of Houseflies to γ-Benzene Hexachloride and Dieldrin

Abstract

THE following observations have been made during a study of the mechanisms of resistance to γ-benzene hexachloride in a strain of Musca domestica obtained initially through the kindness of Dr. J. R. Busvine. The flies (S-flies) had a history of dieldrin resistance¹; but the first generation of adults at this Laboratory were found to be only slightly more resistant to dieldrin and γ-benzene hexachloride than the normal Laboratory culture of Musca domestica. On incorporation of graded amounts of dieldrin into the larval medium of the S-flies the level of resistance rose rapidly. After six generations a concentration of 150 p.p.m. of dieldrin per wet weight of larval medium had been attained, and this concentration has been maintained during subsequent generations. These flies (R-flies) were highly resistant to both dieldrin and γ-benzene hexachloride although at no time has the latter been used for selection at this Laboratory.