The resistance to desiccation of Drosophila mutants affecting body colour

Abstract

The offspring of a $\frac{y}{y^{+}}$ $\times $ $y$ cross in Drosophila melanogaster, simulans, subobscura and pseudoobscura race A showing phenotypically yellow body colour die earlier when starving in dry air (0% relative humidity and 25 degrees C) than flies of wild type body colour which differ in respect of one gene. The yellow flies also lose more weight. In D. melanogaster $F_{2}$ flies of black or ebony body colour survive longer and lose less weight under these conditions than their wild type sibs. These differences are smaller at 70% relative humidity, and disappear at 100% moisture. In the presence of drinking water, yellow females of all four species frequently survive longer than wild type females. It is suggested that most of these differences in survival time and loss in weight may be due to differences in the resistance to evaporation, which can be assumed to vary with the body colour. This assumption is supported by recent results of Fraenkel and Rudall (1940). Secondary differences due to differences in melanogenesis are discussed. The ecological meaning of these findings is under investigation.