Dec. IS, 1919 Apple-Grain Aphis 313 



REPRODUCTION 



The average number of young produced by seven stem mothers was 

 99, in an average of slightly less than 19 days. The greatest number 

 produced by one insect was 131 in 20 days; the least was 51 young pro- 

 duced in 7 days, an average production of 7.27 young per day. This 

 was the greatest average daily production by any one stem mother. 



The actual number produced per day varied from none to 16. There 

 was no imiformity in the frequency of the births, some insects depositing 

 large numbers in a short period and resting for some time between these 

 periods, others depositing a few each day. 



One insect gave birth to 22 young, all of which were deposited with un- 

 ruptured membranes. None of these insects lived more than 24 hours. 

 None of the other mothers produced young in this condition. 



A second adult produced 80 young in 10 days.* She was injured on 

 the eleventh day, her abdomen being slightly crushed. While she lived 

 for 14 days after the accident and appeared perfectly normal, she failed 

 to produce any more young. The abdomen attained its normal shape 

 within 24 hours, and the insect fed normally. 



In most cases the abdomen began to shrink toward the end of the 

 reproductive period, and the mother lived but one or two days after produc- 

 ing her last young. In fact some died almost immediately. In two cases, 

 however, no shrinking was apparent. It was noticed that toward the 

 end of the reproductive period the abdomens of these two insects were 

 becoming darker and irregularly mottled. One of these insects lived for 

 13 days after producing her last young, while the other was fixed for 

 sectioning after a period of 1 7 days. Both continued feeding throughout 

 the period, and neither showed the least sign of shrinking. When the 

 preserved specimen was sectioned, it was found that the reproductive 

 system had almost entirely disintegrated. Three embryos were present, 

 but these also were disintegrating. The digestive tract was apparently 

 normal. The abdomen was almost entirely filled by the fat body, 

 which extended well into the thorax. The injured specimen which has 

 been mentioned suffered the same color changes that these two insects 

 did, and although no examination was made it seems possible that the 

 conditions occurring in these two insects were produced artificially in the 

 third aphid through injury. 



FEEDING HABITS 



During the spring of 1915, as has been stated, some eggs hatched as 

 early as March 15. At this time the apple buds had not begun to swell. 

 These early individuals were all killed shortly after emergence by a return 

 of low temperatures, and it was impossible to determine whether or not 

 they might have lived on the unopened buds. 



' This average of eight youn^ per day was not considered in obtaining the figures given, since the insect 

 did not complete her reproduction period normally. 



