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. 



lic^c^^^^^H:^** 



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 aeerifolii 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 aeerifolii 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 tvinged forms on the 

 alder leaves at the time it was taken seemed puzzling, as no 



