Puant Lice Inyurtinc FouiaGE AND FRuiItT oF THE APPLE 751 
and April 15 (1918). Hatching continues over a considerable period, usually 
about ten days if the weather is favorable. The stem mothers become 
mature during the last few days of April and the first week of May. 
In some years this plant louse is extremely abundant and may be found 
in great swarms on the opening apple buds. Since the stem mothers hatch 
at the time of the swelling of these buds, the lice may be found congregated 
at the very tips seeking entrance even before the tips show green. As the 
buds unfold, the lice feed indiscriminately on the tender foliage but do 
not cause any marked curling of the leaves. Altho the lice were extremely 
abundant in 1915 they did scarcely any damage. Undoubtedly they 
reduced the vitality of the foliage to some extent, but not enough to 
be noticeable as compared with the injury caused by Aphis pomi and 
A. sorbt. 
The stem mother 
In the species Aphis avenae the stem mothers reach maturity in about 
two weeks after hatching from the eggs. They feed almost exclusively 
on the opening foliage but do not cause any curling. They never attack 
the tender twigs, and have never been observed feeding on the water 
sprouts as is so common with the green apple aphis. The stem mothers 
become mature early in May. Altho a large number were reared in 1915, 
only a few were successfully carried thru the productive period. Deposi- 
tion of young usually begins within from twenty-four to thirty-six hours 
after the last molt. In the individuals carried thru a normal life, the 
productive period was 30 days, the total production of young averaged 75, 
and the average daily production was 2.58. The total length of life was 
44 days. 
Description of stages 
First instar (Plate XVIII).— The young nymph is dark green in color, 
with slightly lighter green down the middle of the dorsum; the head . 
bears two black quadrangular areas on the dorsal surface, separated 
along the middle by a dark green line; the antennae, the legs, and the 
cornicles are almost black. The antennae are short, reaching to about 
the end of the thorax (fig. 111, c, page 684). The cornicles are very short, 
forming scarcely more than prominent disks (fig. 111, c). These last two 
characters readily separate this nymph from those of the other two species. 
