754 RoBerT MATHESON 
(fig. 114, B, page 705). The length of the antennal segments and the 
number of sensoria are as follows: Segment III, 0.3 mm., sensoria 8-10; 
Segment IV, 0.19 mm., sensoria 6-8; Segment V, 0.16 mm., sensoria 1; 
Segment VI, 0.1 + 0.35 mm., sensoria the usual group. 
Summer life history 
At Ithaca only three generations are normally produced on the apple. 
The winged migrants have practically all left for their summer host plants 
early in June, a few stragglers being found up to the end of that month. 
These summer host plants consist of a large number of grasses and culti- 
vated grains; a full list is given by Davis.” 
During the summer a large number of wingless and winged generations 
are produced. Late in the autumn, with the approach of cold weather, 
a winged migrating form appears, and this returns to the apple. At 
Ithaca these fall migrants begin to appear on apple and hawthorn about 
the last week in September. From that time to about the last week in 
October they continue to appear in increasing numbers, often in swarms. 
Their maximum flights probably occur about the last week in October. 
At that time they alight in great numbers on almost any object. They 
seem to be partial to white objects, and on examining white clothing 
hung out to dry it is very common to find on it great numbers of these! 
lice. ji 
The fall migrant 
The fall migrant of Aphis avenae is more active than that of A. sorbz, 
and normally is found in much greater abundance. It continues to 
appear later in the season and settles in great numbers on apple and haw-) 
thorn species. The first migrants are all winged viviparous females, and, 
as soon as they reach their food plants they settle on the underside of the) 
leaves and feed. The males begin to appear about a week to ten days| 
after the first females. Deposition of young begins usually within a day| 
or two, and small colonies are soon found settling down close around 
the winged forms. Several such colonies can be readily found on a| 
single leaf. As the season advances these colonies become more and| 
more abundant. | 
% Davis, J. J. The oat aphis. U.S. Dept. Agr. Bul. 112:1-16. 1914. 
