328 
Journal of Agricultural Research 
Vol. VII, No. 7 
the weather is favorable, the first instar will be much shortened. The 
total nymphal life averaged in the experiments 15 days, and this was the 
average in spite of the variation in the length of the instars. 
REPRODUCTION 
The stem moth.ers began reproducing in the experiments during the 
24 hours following the last molt. Considerable variation was noted 
amongst individuals, both as to the total number of young produced and 
the number produced daily. Reproduction in groups, as has been noted 
by the authors for Aphis pomi , is very common with this species also. 
The greatest number of young produced by any individual stem mother 
was 260, and these were produced during a period of 20 days. The 
smallest number produced by one adult was 81 in 24 days. The average 
number for 12 individuals was 71.1 young each, the average reproductive 
period being 26.3 days. The average daily production was 6.3 per insect 
and the greatest record was 14.6, one female giving birth to 44 young 
in 3 days. 
LONGEVITY 
The greatest length of life observed was 45 days. Many other stem 
mothers which died from accident before an equally long period of time 
were in very good condition at the time of their death. It would 
seem, therefore, that this period is not very far above the average. 
SPRING FORMS 
Several generations of aphids, in which both wingless and winged 
forms occur, follow the stem mother upon apple. In 1914 five apple- 
infesting generations occurred in the experiments, while in 1915 seven 
such generations were observed. In both cases the first stem-mother 
generation is not included in the figures given. 
The first of these generations, the second generation from the egg, 
appears to be composed entirely of wingless insects—at least there were 
no winged forms in the experiments, either in 1914 or 1915. In the third 
generation, however, a few winged forms occurred and the percentage of 
winged to wingless insects increased rapidly up to the sixth generation 
in 1914 and the eighth in 1915, in which all the adults had wings. Two 
intermediates were also reared with the spring migrants. 
SPRING WINGLESS VIVIPAROUS FEMALE 
description 
First instar. —Morphological characters. Antennae with the following measure¬ 
ments: Segment III, 0.16 to 0.208 mm., average 0.182 mm.; IV, (0.048 plus0.176 mm.) 
to (0.072 plus 0.224 mm.), average (0.059 plus 0.204 nun.). Cornicles about 0.088 
mm., rather short and thick. 
Color characters: General color light yellow; about the base of each cornicle a small 
reddish patch. Eyes dark red or brownish; cornicles dusky. Legs pale yellow with 
the tarsi and possibly the distal extremities of the tibiae dusky to black. Antennae 
