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 
erass as one of its midsummer food plants. While in this and other 
cases we have been unable 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 asingle 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 natal 
enemies. 
Dr. Cyrus Thomas states that in 1875, in Southérn 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 188889 was a mild one, but 
we were absent in Australia during the entire time. 
Siphonophora avene 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 earried 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 nnmbers to affect the plants. This species occurs 
Penquekony fhe: entire State, from about the last of Bepleniney and 
* Eighth Rep. ‘St. Ent. MN, 1879, p- 53. 
a eee 
