82 
The Ohio Naturalist. 
[Vol. XIII, No. 5, 
respiratory appendage (Figs. 84, 85) is a fourth longer than broad, 
testaceous brown, ringed about mid-length, thence slightly 
constricted. The spiracles (a) moderately long, somewhat ele¬ 
vated above the surface; the inter-spiraeular spines (b) short, 
blunt, spur-like, rather prominent. Dorsal spiracular spine (c) 
short, compressed; its breadth about equal to diameter of the 
approximate circular plate ( d ). 
These larvae were found, full-grown, at Cedar Point, July 7, 
1911. The larval stage continued indoors to July 11 and 12. 
They were collected on the Poplar or American Aspen 
(Populus tremuloides Mx.) in the well-known, characteristic galls 
on the ends of the twigs, made bv the aphid, Pemphagus vagabundus 
Walsh. 
These galls are large, commonly two inches in diameter, very 
irregular in shape, the outer surface thrown into numerous deep 
convolutions. Their structure is such that they enclose a number 
of small, partially separated chambers, the thick walls of which are 
lined by the aphids. 
There are usually several openings to the many-chambered 
gall, but it is pretty certain that the larvae do not ordinarily 
migrate from gall to gall; although there is a bare possibility that 
they might do so if the food supply in any one ran out. They 
are negatively heliotropic, seeking out protected dark comers 
when kept in confinement. They feed on the body contents of 
the aphids; hence there is commonly an abundance of food at 
hand and, as the volume of the chambers in the gall is small, there 
is no occasion, and little opportunity, for active movements. In 
correlation with this we find the larvae very sluggish, lying quietly 
for hours or even days, even though unfed. Since migration 
from one of these galls to another would commonly involve trav¬ 
eling for several feet, it seems to me very likely that the larva or 
larvae are dependent on the aphids within the single gall in which 
they begin their larval existence. They are very well protected 
within the poplar galls and I found no parasites affecting them. 
It would seem that they are paying for their well-fed, well-pro¬ 
tected, sedentary life in sluggishness, and are possibly on the road 
to degeneration. 
Pupa. 
Dimensions, average of 5: Length 7.2 mm., height 3.5 mm., 
width 3.8 mm. These puparia (Figs. 8G, 87) are exceptionally 
inflated dorsally, the ratio of height to length being greater than 
in any of the other species I have examined. It is characteristic of 
them also that the posterior inflation is equal to, or greater than, 
that anteriorly; in outline, as seen from the side, the dorsal half 
of the puparium makes an almost perfect semi-circle. The ven¬ 
tral line is sinuate. The respiratory appendage (a) projects from 
