74 Annals Entomological Society of America [Vol.11, 



Mr. Phillips in a long series of breeding experiments carried 

 out at Richmond, Indiana, has found that the oviparous 9 

 will not deposit eggs without having first mated with the d*, 

 and usually produces not more than five or six eggs. The 

 life of the viviparous 9 is much longer than that of the oviparous 

 9 but the life of the latter is greatly prolonged if she fails to 

 meet the d^ and become fertilized. 



HIBERNATION. 



The species will breed at about or a little above 45° Fah., 

 though, as determined by Mr. Phillips, they do not reach their 

 maximum until the temperature rises to above 50° Fah., which, 

 however, is still too low to render their parasites active. As an 

 experiment, a miscellaneous lot of individuals were frozen up in ice 



Fig. 4 — Spring grain-aphis {Toxoptera graminum: Male. 

 Greatly enlarged. (Original.) 



for five, twelve and twenty-four hours respectively, and on being 

 thawed out the older individuals all succumbed ; in another twen- 

 ty-four hours experiment, using individuals of different stages 

 of development, only the pupae of the viviparous 9 survived. 

 Viviparous 9 9 brought indoors from a temperature of 11° Fah., 

 and thawed out began to give birth to young in about three hours. 

 Thus it is that the species is able to withstand the climate of 

 northern latitudes and high altitudes. As it breeds freely in a 

 temperature of 100° Fah., in the shade, presumably still higher 

 in the open, on the public grounds in Washington, it would seem 

 that farther south, where it was found by Mr. C. N. Ainslie, the 

 insect would encounter even a greater degree of heat in summer. 

 Thus we have a fairly good basis for the supposition that it 



