The Effects of High Temperature on Bristle Frequencies in Scute and Wild-Type Males of Drosophila Melanogaster.

URING the past twenty-five years there has appeared a considerable D amount of literature concerned with temperature-effective period studies on mutant races of Drosophila melanogaster. Adult characters which have drawn the most attention have been the compound eye, the wing, and the bristles. Most of the work on the eye has been done with Bar and its alleles (see especially DRIVER 1926 and 1931, LUCE 1931, and MARGOLIS 1935). Wing studks have been confined largely to vestigial and its alleles (see especially RIEDEL 1934, STANLEY 1935, HARNLY 1936, HARNLY and HARNLY 1936, and LI and TSUI 1936). The bristle studies have been on the bristle-removing genes, Dichaete (PLUNKETT 1926) and scute (CHILD 1935 and 1936, IVES 1935). It has been found to be general in most of these studies that under the conditions of the experiments the adult expression of these several mutants is affected by a change in developmental temperature over the viable temperature range (14' to 31'C) during only a limited developmental period. This period has come to be known as the temperature-effective period (TEP) of the mutant character. This paper reports a series of experiments on scute (sc) using brief exposures to lethal temperatures (36' and 4oOC). A preliminary account of part of this work has already been published (IVES 1935).