Experiments on Toleration of Temperature by Drosophila. by Harold H. Plough Ai~-d

In connection with experiments by one of us on the effect of high temperature on the amount of crossing over in Drosophila it became obvious that differences exist among various cultures of this fly in the ability to withstand temperatures above the normal range and in the ability to breed at these temperatures. A series of comparative tes ts was therefore undertaken in order to gain more accurate information along these lines. Experiments on a single culture of Drosophila melanogaster, grown on sterile yeast medium, were reported by Northrop I in 1920. He wished to find out whether the offspring of cultures kept at high temperatures acquired the ability to tolerate temperatures still higher. He found that no such adaptation occurred, and that fries could be carried at temperatures above 29°C. for one generation only. These flies would however breed normally according to his findings if returned to normal temperatures for a period of 24 hours. Since Northrop's work was upon a single stock of Drosophila only, it seemed of interest to us to determine whether there was not a difference in the upper temperature limit among different cultures of Drosophila, which might be genetically determined. Our work indicates that with optimum food conditions it is only the exceptional stock of Drosophila mdanogaster which will not breed at 31°C. Furthermore our work suggests the basis for the failure to breed at high temperatures as observed by Northrop and by ourselves.