An investigation of relationship of body colour and susceptibility to DDT in Drosophila melanogaster.

There are a series of mutants of melanogaster which affect body coloration. Kalmus (41) has stated that he has found a relationship among these mutants between colour and susceptibility - namely that the darker cuticle - (a) gives better protection from desiccation. (b) absorbs and loses more heat. (c) is less easy to wet. (d) is tougher and mechanically more resistant. Kalmus (42) has shown experimentally that the yellow mutant of Drosophila melanogaster is more susceptible to dessication, and that the black mutant is more resistant than the wild type to - (a) dessication (b) exposure to a mixture of pyrethrum extract and sulphuric acid. If this is so, we might expect a similar situation when a contact insecticide is applied to these various mutants. This might be so, particularly in the case of D.D.T. (2.2. bis dichlorophenyl 1.1.1. Trichlorethane) as - (a) it has been shown to act by penetration of the chitin, and (b) flies killed by D.D.T. appear extremely dessicated at death. Evidence that D.D.T. acts as a contact insecticide has been derived from several lines of investigation. [...