APHID PESTS OF AIAIXE, H. WILLOW FAMILY. 75 



parasitic insect or fungous attack. Winged form and pupae were 

 present in other galls, and a species of Cha'tophoms was 

 populating galls deserted by this Pemphigus. 



86-06. Populus balsamifera. July 26, 1906. \'eazie, 'Sle. 

 A single winged specimen in each small gall except where the 

 gall was already vacated or occupied by a syrphus maggot. 



81-09. Populus balsamifera. July 22-27, 1909. Veazie, 

 Me. Galls very numerous. A single leaf was found bearing 

 65 galls. Four stem mothers, numerous pupae and winged 

 migrants still in galls, — each solitary. 



99-12. Popuhis balsamifera. July 18, 1912. Veazie, Me. 

 Galls numerous each containing a single insect in pupal stage. 



Pemphigus gravicornis n. sp. For the past three years the 

 pseudo-galls of this species have been common on Populus bal- 

 samifera. The afifected leaves are folded lengthwise along the 

 midrib and their margins are applied together at their ventral 

 surfaces. The whole leaf except at the margin is swollen into 

 a large sac or pocket which is filled with aphides. Fig. 53. 

 This gall resembles that of populiconduplifolii but the two 

 aphides are readily separated on antennal characters. So far 

 as my observations go the galls of gravicornis occur on leaves 

 anywhere on the tree while those of populiconduplifolii are on 

 terminal leaves only. 



Winged viviparous form. — Spring migrant, with antennal 

 joints III, IV, V heavily charged with large irregular sensoria 

 giving them a knurled appearance ; and Vl very slender and 

 ordinarily without sensoria except the usual one at base of 

 spur, though one or more others may be present. Fig. 23. 



Fig. 23. P. gravicornis. Antenna of spring migrant. 



The wings are delicate and the veins faint. Fig. 46 H. No 

 description has been made of the living specimens, but the 

 peculiar antennae will serve to distinguish this species. 



Collection data are as follows : 



87-06 July 26. 1906. A'eazie, ]\Ie. ; 26-11 July 7, 191 1, Orono, 

 Me. ; 98-12 July 18, 1912, Veazie, Me. Pup^e and migrants 



