PARTHENOGENETIC PURE LINE OF APHIS AVEN/E FAB. 99 



place at ordinary temperatures if the temperature is kept 

 constant. 



3. As to Rate of Reproduction At 60 F. the average rate of 

 reproduction was 2.2 births per day per individual. At 70 F. 

 the rate was 3.7 per day per individual. At 80 F. the rate was 

 6.1 and at 90 F., 0.25. Therefore, we conclude that temperature 

 affects the rate of reproduction in a most fundamental way; that 

 about 80 F. is the optimum temperature for reproduction; and, 

 that the optimum for reproduction is quite different from the 

 optimum for growth, at least as far as the wingless forms are 

 concerned. 



4. Effect on Mortality. The mortality percentages for the 

 different constant temperatures were: 60 F., 72.7; 70 F., 70.3; 

 80 F., 24.6 ; 90 F., 100. Obviously, the extremes of temperature 

 are quite disastrous to Aphis avence. At 60 F. we find that almost 

 3 out of 4 die before reaching maturity. At a constant tempera- 

 ture of 90 F. not a single individual reached maturity. This 

 observation coincides well with observations in general of special- 

 ists in the Aphididce, who report the disastrous effects of hot sum- 

 mer weather on our injurious species. The optimum for the 

 least mortality appears to near 80 F., but probably it is slightly 

 below this point. 



THE EFFECT OF FASTING, DURING THE GROWTH PERIOD, ON THE 



SIZE OF ADULTS. 



The abundance of food during the growth period of an insect 

 is known frequently to affect the size of the adults produced. 

 It occurred to me that probably fasting periods of different lengths 

 during the growth of individuals of Aphis avencB Fab. might affect 

 the size of the adults. In order to test this point, 33 young 

 nymphs, born between 6:00 and 12:00 A.M. (average time of 

 birth 9:00 A.M.), were placed in different lots in four different 

 breeding cages, but under similar conditions, and were deprived 

 of food for different periods. The individuals of all lots were 

 allowed to feed for 24 hrs., then they were deprived of food for 

 the following periods: Lot I, 4 hrs.; lot 2, 8 hrs.; lots 3 and 4, 

 24 hrs. At the end of these fasting periods it was found that the 

 individuals of lots 3 and 4 were dead. The others endured their 



