Dec. 15, 1919 A pple-Grain A phis 319 



LONGEVITY 



The average length of life for 98 insects was a little over 28 days. In 

 general the mothers died on the day on which they produced their last 

 young. Toward the end of the season, however, several insects lived 

 for a period of from four to nine days after reproduction had ceased. 

 This was apparently due, in part at least, to the fact that reproduction 

 was not so rapid during this period as it was earlier in the summer and 

 the mothers were not completely exhausted as were the others. 



SUMMER intermediate; form 



As has been stated previously, the summer intermediate form occurred 

 in only five experiments. Young were reared from only two mothers, 

 and these were both preserved for microscopical examination before they 

 had completed their reproductive period. From our meager records it 

 appears that the length of nymphal life is equal to that of the alate form. 

 Such is the case, at least, in the five experiments under consideration. 

 On the other hand, the reproductive activities appear to be patterned 

 after those of the apterous aphids. One of the intermediates pro- 

 duced 1 7 young in six days and was then preserved. The body still con- 

 tained numerous embryos, indicating that normally it might have 

 produced as many youn;;^ as the average, at least, of the apterous insects. 



summer alate form 



LENGTH OF IMMATURE STAGES 



Like the spring migrant, the summer alate form required from iX to 

 2 days more for the attainment of the adult form than did the apterous 

 aphids. The record for 14 insects gives a period varying from 9 to 12 

 days. In each case this was about 2 days longer than was required by 

 apterous insects in the same experiment. 



REPRODUCTION 



Complete records of the reproductive activities of this form were ob- 

 tained for only 8 insects. These 8 produced an average of 16.25 young 

 per mother. The greatest number produced by one insect was 23, while 

 the smallest was 12. The average length of the reproductive period 

 was II. 9 days, varying from 7 to 20; and the average daily production 

 for the 8 insects was 1.36 young per mother per day. 



LONGEVITY 



The average length of life of the 8 insects just mentioned was 22.2 

 days. In all but 2 cases the mothers died upon the day on which they 

 produced their last young. These 2 insects each lived for 2 days after 

 reproduction ceased. 



