Eriosoma americanum (Riley)

Spring colonies on Ulmus americana roll the edges of the leaves downwards (see influentialpoints.com/Gallery). Emigrant alatae (fig.118C) emerging from galls in June are dark green to blue-black with some wax wool, and rather dark wing veins; BL 2.0-2.5 mm. They migrate to form colonies of pale pink, woolly apterae on roots of Amelanchier. Return migrants to elm in August to October produce dwarf sexuales that lay overwintering eggs on bark (Patch 1915a, Palmer 1952). It occurs throughout the natural range of U. americana in eastern North America, and in the west on planted elms.

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

Reference: http://www.aphidsonworldsplants.info/d_APHIDS_E.htm#Eriosoma