746 ROBERT Macrmso 
number of natural enemies which this aphid encounters on the plantain 
seems to necessitate a high productive capacity, which the species possesses, 
and also ability to spread to more distant host plants. 
Habits of the summer forms 
The summer forms on the plantain are much more active and agile 
than those occurring on the apple. Their legs are relatively longer when 
compared to the length of the body, and they can run with great rapidity. 
If an infested leaf or flower stalk is Jarred or moved, the aphids at once 
remove their beaks and scurry rapidly for cover or drop to the ground. | 
On the ground they hasten away and can travel considerable distances. 
In several rearing cages the aphids became so abundant that they caused 
the death of large plants. In such cases they climbed about the inside 
of the cage in immense numbers, endeavoring to find any possible exit. 
When the cages were opened they ran out very rapidly, and if they escaped 
their natural enemies it was not long before another plant was found. 
Undoubtedly this is the common way in which the species spreads from 
plantain to plantain during the summer. 
Description of stages 
Summer. wingless viviparous female, adult— Length 1.4-1.6 mm.; 
width 0.8 mm.; cornicles 0.4 mm. long. 
The general color is light lemon yellow, usually with a faint reddish 
tinge on the dorsum of the metathoracic segment, and reddish yellow to 
reddish around and between the cornicles; in older specimens the color 
may become almost brown; the distal parts of the antennae, and the 
cornicles, the eyes, and the tarsi, are black. The antennae (fig. 114, p, 
page 705) are 6-segmented, slender, long, reaching beyond the tips of the 
cornicles. The segments are imbricated, ana ‘ack sensoria except an 
apical one on Segment V and the usual group at the distal end of the basal 
part of Segment VI. The length of the segments is as follows: Seg- 
ment III, 0.4 mm.; Segment IV, 0.32 mm.; Segment V, 0.24 mm.; Segment 
VI, 0.12 + 0.836 mm. The head has a faint median tubercle; the dorsal 
tubercles are absent; the abdomen and the thorax lack the lateral and 
dorsal tubercles so prominent in the forms on apple. The cornicles are 
cylindrical, slender, slightly curved, and distinctly flanged (fig. 115, p, 
