The hypothesis that genetic homeostasis breaks down to yield greater genetic variance in more stressful environments was examined. Environmental stress was measured by mean development time and by wing length, it being expected that more stress generally gives rise to longer development times and shorter wings. The correlations between mean values and genetic variance were predicted to be positive for development time and negative for wing length. The correlations were not always statistically significant, but were in the predicted direction in 7 out of 8 tests. Quite possibly this phenomenon contributes to observed increases of genetic variation in marginal environments and more rapid evolution during periods of special stres
