194 



WILLIAM C. YOUNG AXD HAROLD H. PLOUGH. 



contained five pairs of flies each, so that individual differences 

 are largely eliminated from the result. The time of the appear- 

 ance of the first eggs and first larvae are noted in each case, and 

 the data are tabulated in Table III. 



TABLE III. 



CANTON STOCK CULTURES STERILE AT 31, REMOVED AND PLACED AT 24. 



For the cultures recorded in Table III. the date of the first 

 adult flies was recorded also, but is not noted in the table since 

 the average number of days between the appearance of larvae 

 and the emergence of images was the same in all cases about 

 six days. The second line in the table affirms the result given in 

 Tables I. and II., namely that females are not affected by a tem- 

 perature of 31 degrees and their eggs develop as soon as fertilized. 

 The remainder of the table therefore indicates the effect of the 

 high temperature on the male flies. The females begin to lay 

 eggs at once, but they do not lay eggs which develop until a period 

 of seven to nine days has elapsed. The time when fertile eggs 

 begin to be laid bears only a slight relation to the length of 

 exposure to high temperature after hatching, but the last column 

 showing the number of cultures which failed to recover, indicates 

 that more males never regain fertility after a longer exposure. 



