70 



We have several times attempted to follow the species through July 

 and August, but have always failed. Adults placed on various kinds 

 of grasses in breeding cages invariably died during July. The occur- 

 rence of great numbers of wingless parasitized females on heads of 

 Poa pratensis, long distances from grain fields, strongly suggest this 

 grass as one of its midsummer food plants. While in this and other 

 cases we have been uDable to rear Aphides on certain plants in breed- 

 ing cages, yet we do not feel at all certain but that outside, under the 

 usual environments, nature might accomplish precisely the same object. 

 The results of breeding cage experiments with Aphides must always be 

 accepted with extreme caution. 



The present year we had young grain growing continually from spring 

 to November, yet not a single grain Aphis was to be found on either 

 this young grain or grasses from July 9 to late in October. Their 

 limited numbers at this season may, however, be accounted for by the 

 fact that they were very nearly exterminated in July by their natural 

 enemies. 



Dr. Cyrus Thomas states that in 1875, in Southern Illinois, he ob- 

 served winged and wingless specimens on wheat during winter, and 

 suggests that the species winters over in other forms than the egg.* 

 There appears to be no good reason for doubting the truth of Dr. 

 Thomas' suggestion, especially if applied to mild winters. During the 

 time we have been located in a wheat-growing district the winters have 

 been quite severe, so that we have not been able to follow the species 

 through the cold months. The winter of lSS8-'89 was a mild one, but 

 we were absent in Australia during the entire time. 



Slphonophora avenw is by no means the only species of Aphides in- 

 festing the plants of our smaller cereal grains. An undescribed species 

 of Toxoptera occurs on the leaves of wheat in the latitude of La Fayette, 

 in June. We have carried this species through July and August on 

 wheat in breeding cages, found it again in the fields in September, and 

 from this on until the 22d of December. During the latter month they 

 continued to reproduce in a room, which, though warm during the day, 

 the temperature fell below the freezing point every night. I have not 

 been able to follow the species through the winter months in the fields. 



A species of Aphis, undistinguishable from A. mali, appears regularly 

 every September, and, indeed, sometimes as early as July 17, on young 

 wheat and rye. From the latter date up to the 12th of November they 

 have been observed on young grain, giving birth to their young. 



Notwithstanding the fact that the species is not distinguishable from 

 the apple tree Aphis, yet the attempt to transfer them to the apple leaf, 

 or vice versa, has invariably resulted in failures. 



A second Aphis, as yet undescribed, is found about the roots of wheat, 

 often in sufficient numbers to affect the plants. This species occurs 

 throughout the entire State, from about the last of September, and 



* Eighth Rep. St. Eut. 111., 1879, p. 53. 



