736 RoBpertT MATHESON 
antenna yellow, remainder black; legs yellow, the distal ends of the 
tibiae, and the tarsi, black; cornicles yellow, tips black. 
Winged viviparous female.— Length 1.44 mm.; width 0.8 mm. ; cornicles 
0.24 mm. long; wing expanse 5-6 mm. 
The head is black, with the tubercles on the vertex prominent. The 
eyes are red to almost black, and tuberculate. The antennae are 6-jointed ; 
the color is black except for the two basal segments, which are fuscous. 
The thorax is shining black. The base of the femora is banded with 
yellowish, the remainder is black; the tibiae are yellowish brown, with 
the distal ends black; the tarsi are black. The abdomen is yellowish 
brown at the sides and the base, with the dorsal part fuscous to black; 
around and between the cornicles the color is reddish yellow. The cornicles 
are cylindrical, gradually tapering, somewhat flared at the tips, black. 
The cauda is short and fuscous. Lateral tubercles are present on the 
prothorax and on all the abdominal segments except the seventh and the 
eighth, each of which bears two dorsal tubercles, one on each side of th 
median line.. 
The third generation 
In 1915 the descendants of the second generation — that is, the thir 
generation — began reaching maturity on June 12. In the writer’s larg 
rearing cage, where the seedling trees had become very’ crowded wit 
the plant lice, the majority of the insects, in fact nearly all, acquire 
wings and migrated to their summer food plant. However, many di 
not acquire wings and these began producing another generation on th 
apple. The writer’s observations in the field during the past season (1917 
led to the conclusion that the majority of the lice of this generation di 
not acquire wings but settled down and produced a fourth generatio 
on the apple. When such conditions occur there results a serious infesta 
tion, with consequent damage to foliage and fruit. 
In 1915 the wingless females of the thi.d generation began producin 
young on June 12, and the productive period extended well into July) 
In the case of five normal individuals the average producing period wa 
22.6 days, while the daily production averaged 5.69. The productiv 
capacity averaged 127.4, which is considerably lower than that of th 
stem mothers but somewhat higher than that of the second generatio 
The habits and activities of the third generation do not differ fro 
