ENVIRONMENTAL EFFECTS 



ture for hatching to be 29° C, the optimal rel- 

 ative humidity, 80 per cent. The time required 

 for hatching is increased by lower temperatures 

 but is not noticeably influenced by relative 

 humidity except at 19° C. and below, when lower 

 relative humidity slows up development. At op- 

 timal temperature egg mortality is not signifi- 

 cantly influenced by relative humidity; at low 

 or high temperature it is increased by low rel- 

 ative humidity; at optimal relative humidity it 

 is low through a wide range of temperatures (16- 

 35° C.) but rises quickly to 100 per cent near 

 the lower and upper limits (12° C. and 38° C). 



Temperature treatment of mated females slight- 

 ly affects the sex ratio of offspring, the most 

 significant decrease in female ratio being ob- 

 served at constant low or high temperatures. 

 Short time exposure of heterozygous females to 

 extreme cold does not significantly affect the 

 rate of production of male mosaics and gynan- 

 ders. However, when such females are placed at 

 a constant low temperature, no mosaic offspring 

 appear. On the other hand if females are kept 

 at 35° C. to 37° C. a significantly greater num- 

 ber of mosaics appear (Greb, 1933c). 



Experiments with crosses of closely related 

 stocks show that the percentage of diploid males 

 decreases as culture temperatures are increased 

 (P. W. Whiting and Anderson, 1932). Females 

 mated with related males produce fewer biparen- 

 tal offspring if kept at 30° C. than if kept at 

 20° C. However, at the higher temperature, the 

 percentage of diploid males is greater. Trans- 

 fer of young to other temperatures appears to 

 -lave no effect on ratios except that the ratio 

 qtf biparentals is increased if transfers are 



127 



