Feb. ax, 1916 
Green Apple Aphis 
973 
September the temperature dropped below 50° F. several times, reaching 
37 0 in one instance. These extreme temperatures were of short duration, 
however, and the mean was never below 50°. By the end of October 
the nymph required 12 to 14 days to attain the mature condition. At 
times during this month the temperature averaged between 53.5 0 and 59 0 
for periods of 24 to 36 hours. During such periods very little feeding or 
growth took place. The insects would stand perfectly motionless. 
Mechanical stimulus with a needle merely induced slight movements of 
one or two legs. Moreover, it required considerable time for the insects 
to recover from such conditions, and often maximum temperatures of 
65° to 70° would not cause a resumption of active feeding. 
The difficulty of exactly correlating the rate of growth with temperature 
conditions is greatly increased by the fact that the condition of the food 
supply was as great or even a greater factor in determining this rate of 
growth. This factor can only be appreciated, however, in marked cases. 
Usually the observer is unable to determine which of two plants offers the 
insects the best food, and consequently is unable to gauge the proper 
values of the two factors. The effect of the food condition is taken up 
more fully in another place (p. 983). 
REPRODUCTION 
As in the stem mothers, the wingless viviparous females begin repro¬ 
duction about 24 hours after becoming mature. In fact, this condition 
obtained for all viviparous females, whatever the form. 
The average reproduction varies greatly during the season and the 
writers find that their figures separate into three well-defined groups: First, 
reproduction by the summer forms bom before July 1, and reproducing 
by July 6; second, reproduction by forms bom between July 1 and Sep¬ 
tember 1, beginning to reproduce between July 6 and September 10; 
third, forms bom after September 1, commencing reproduction after 
September 10. Eighty wingless individuals in the first group produced 
an average of 55.4 young per insect; 113 wingless individuals in the sec¬ 
ond group averaged 30.9 young, while in the third group 24 wingless indi¬ 
viduals averaged 12.1 young apiece. The last mothers of the season 
produced only from 1 to 4 or 6 young. The average reproduction per 
insect per day during the first period was 2.95, during the second 1.92, and 
during the third 0.83. 
For the entire season the average per wingless insect was 37.5, and the 
daily average was 2.22.. The greatest number of young produced by one 
individual was 133, while the maximum reproduction for one day was 
16 -f-, one insect producing 64 young in 4 days. 
The rate of reproduction was very irregular. In some cases the major¬ 
ity of young were produced early in the life of the adult. In others com¬ 
paratively few were produced during the first few days and then large 
