486 ENTOMOLOGICAL NEWS. [Dec., ’08 
in laboratory. They settled contentedly upon the twigs. Aug- 
_ust 30. The progeny of winged P: tessellata placed on the 
maple twigs in laboratory are sexual forms proving upon mi- 
croscopic examination to be exactly like those collected from 
under bark of maple on campus. 
September 3. Numerous yellow eggs are present under bark 
among the Pemphigus on maple trunks on the campus. 
September 4. Pemphigus tessellata numerous on wing and 
observed floating in the air on campus. Individuals were 
watched and seen to alight on the maple bark where they set- 
tled and sought rough places in the bark. 
* xk * * * X* * * * * * 
We have, then, unquestionably the oviparous females and 
males of Pemphigus tessellata deposited upon maple trunks by 
the winged migrants from the alder and the eggs of this spe- 
cies deposited under the bark of the maple. Coupled with the 
fact that P. tesellata hibernates also in the young apterous vivi- 
parous form among the leaves at the base of the alder clumps 
this would seem rather to complicate matters than to prove a 
missing link. 
On the basis of these observations it seems safe to hazard the 
following guess as a working hypothesis. Pemphigus aceri- 
folii Riley, a flocculent species on maple leaves is very common 
from spring until mid July. A winged generation then appears 
and disappears. Pemphigus acerifolii has been known only 
upon the maple leaf,—the rest of the cycle never having been 
recorded. With this in my mind my aphid notes were searched 
for these two species with the following suggestive coincidence: 
“No. 19-05. Pemphigus acerifolii Riley, Orono. July 15, 1905. 
Winged forms present in great numbers on leaves of maple along river. 
Ready for migratory flight.” 
“No. 30-05. Pemphigus tessellata. Orono. July 18, 1905. Single 
viviparous winged forms scattered about on the alder leaves (mostly 
on under side), followed by a group of young apterous viviparous 
forms present on the alder branches in great numbers, producing 
young.” 
The foregoing record of viviparous winged forms on the 
alder leaves at the time it was taken seemed puzzling, as no 
