Nov. 13, 1916 
Rosy Apple Aphis 
337 
of very rare occurrence throughout the summer, it is not worth while 
to give averages for these very few insects. 
Fifth instar (adult). —Morphological characters. Antennae with the following 
measurements: Segment III, 0.688 mm.; IV, 0.496 mm.; V, 0.304 mm.; VI (0.128 
plus 0.648 mm.). Cornicles 0.352 mm. Segment III with about 58 circular sensoria, 
IV with 34 similar ones, V with 6 or 8 arranged evenly along the segment. Head with 
tubercles above and the last two segments of the abdomen with a pair of dorsal 
tubercles. 
Color characters: Similar to those of the spring migrant, the abdomen above nearly 
uniform brownish fclack or with a distinct patch. 
DIMORPHIC REPRODUCTION 
The writers have already noted in two other species of aphids, A. pomi 
and A . avenae , that the late summer and early fall individuals of the summer 
form may produce two forms of young. In A. malifoliae both summer 
wingless and fall migrants, or fall migrants and males, may be produced 
by one mother. In the experiments the former combination occurred, 
in a general way, earlier than did the latter. Records of the production 
of all three forms by one mother were not obtained. 
As we found to be the case with A. avenae , when one mother produced 
both fall migrants and males, the latter were usually her last progeny. 
FALL FORMS 
Among the fall forms may be included the fall migrant which leaves the 
plantains and flies to apple, the oviparous females which are deposited 
upon the apple leaves by these fall migrants, and the males which fly 
from the plantains to fertilize the oviparous females. 
FALL MIGRANT 
DESCRIPTION 
The early instars of the fall migrant are practically the same as those 
of the summer wingless form. It is therefore unnecessary to give descrip¬ 
tions of any instars excepting those following: 
Fourth instar (pupa). —Morphological characters. Antennae with the following 
measurements: Segment III, 0.4 to 0.464 mm., average 0.427 mm.; IV, 0.288 to 0.344 
mm., average 0.315 mm.; V, 0.208 to 0.24 mm., average 0.227 mm.; VI, (0.096 plus 
0.488 mm.) to (0.112 plus 0.56 mm.), average (0.107 plus 0.518 mm.). Cornicles 0.288 
to 0.320 mm., average 0.305 mm. 
Color characters: Similar to the pupae of the spring migrant. 
Fifth instar (adult) (PI. 21, A).—Morphological characters. Antennae with the 
following measurements: Segment III, 0.624 to 0.800 mm., average 0.689 mm.; IV, 
0.376 to 0.528 mm., average 0.472 mm.; V, 0.256 to 0.336 mm., average 0.308 mm,; 
VI, (0.112 plus 0.56 mm.) to (0.152 plus 0.712 mm.), average (0.132 plus 0.632 mm.). 
Segment III with about 60 circular elevated sensoria, IV with about 27, V with about 
6 sensoria. Head without tubercles above as is usual in the spring migrant. 
Prothorax with very small lateral tubercles. Abdomen also with very small ones. 
Cornicles 0.304 to 0.384 mm., average 0.348 mm. Cauda conical, short; last two seg¬ 
ments of the abdomen without tubercles above as in the spring migrant. Otherwise 
as in that form. 
