Two wild strains of Drosophila and one laboratory strain were selected for resistance to γBHC by a contact method. From each of these three strains equally resistant strains developed in about the same time. They did not become more resistant after prolonged selection. The resistance obtained was further investigated in one of the strains.

There was no evidence of any specificity: the susceptibility of the resistant insects to DDT and “Thanite” also appeared to be less than that of the original strains.

Although the strains were selected by a contact method they also showed decreased susceptiblity when the poison was applied to the skin and when it was injected. From the reciprocal crosses F1's were obtained the susceptibilities of which were practically the same and differed little from that of the resistant parent strain. It follows that resistance does not depend on cytoplasmatic heredity and that it is incompletely dominant.