909] 



Toxoptera graminum and its Parasites 



79 



evidently ready to promptly develop with the advent of warm 

 weather. Mr. Kelly, on the same date, also secured a large num- 

 ber of Toxoptera in various states of development that were hiber- 

 nating in wheat fields near Leavenworth, Kansas. The weather 

 had been such as to preclude the possibility of these having been 

 recently parasitized. Yet some of them soon began to show the 

 characteristic yellow color of a Toxoptera parasitized by Lysiphle- 

 bits, and adults were afterwards reared from them. This shows 

 conclusively that Lysiphlebus hibernates in advance stages of 

 development in the bodies of its host, which they have killed the 

 previous autumn, as well as larvae in hosts wintering over from 

 half to fully grown. 



Fig. 7. — Stalk of wheat, the leaves covered with dead spring grain-aphids 

 killed by the parasite Lysiphlebus tritici. About natural size (original). 



