Pemphigus longicornus Maxson

Galls are elongate, thin-walled, on upper sides of leaves of Populus deltoides. The fundatrix is pale yellowish white. Alatae (BL 1.7-2.1 mm) emerge in May-June and migrate to an unknown secondary host (Maxson 1923). In eastern and southern USA. [According to Smith (1985), there is also an undescribed Pemphigus sp. on P. deltoides in North Carolina that causes elongate to slightly globular galls on the upper sides of the leaves, and has alatae with antennae intermediate in length and antennal sensoriation between longicornus and populivenae.]

- Roger Blackman, Victor Eastop: (2013) Aphids on the world's plants^©

Reference: http://www.aphidsonworldsplants.info/d_APHIDS_P.htm#Pemphigus