Synonyms and other taxonomic changes
Formerly a separate family, Eriosomatidae. Tree of Life
places many (all?) of the included genera in family Pemphigidae.
Cornicles are reduced or absent; sexual forms lack mouthparts (1)
Nearly all members of this subfamily alternate between host plants, generally with a woody primary host (on which overwintering eggs are laid, and on which some species induce galls) and an herbaceous secondary host (1)
Many, but by no means all, root aphids belong to this subfamily. As of 4/12/10, the only non-eriosomatine root aphids on BugGuide are these Aphis (Aphidinae):
includes two species that cause galls on witch hazel. The Manzanita Leaf Gall Aphid
is in subfamily Tamaliinae.
(The following information is based on BugGuide's images and may be modified based on future observations.)
Many woolly aphids are in subfamily Eriosomatinae. However, there are several exceptions (and according to Andrew Jensen, "there are examples of wax-covered aphids in almost all subfamilies."):
The Asian Woolly Hackberry Aphid (Calaphidinae: Shivaphis celti) has red eyes, banded antennae, and distinctively patterned wings.
Birch aphids (Calaphis and Euceraphis), also in Calaphidinae, can be covered with a substantial layer of fuzz:
The Woolly Beech Aphid (Phyllaphidinae: Phyllaphis fagi) forms woolly masses on the undersides of beech leaves (primarily European varieties). We do not have adult images for this species yet.
The Balsam Twig Aphid (Mindarinae: Mindarus abietinus) produces white fluff on fir twigs. Adults have only a thin, light coating of this material.
The Spiny Witch Hazel Gall Aphid (Hormaphidinae: Hamamelistes spinosus), is covered with waxy powder but is not woolly:
The Witch Hazel Cone Gall Aphid (Hormaphidinae: Hormaphis hamamelidis), produces white fluff inside the galls, but the adults apparently have little of this material on them:
Here is one that has been identified as Aphidinae:
Look at wing venation for further clues in distinguishing among these. Below is a Pemphigus (Eriosomatinae) for comparison.
Alleyne, E. H. and F. O. Morrison. 1977. SOME CANADIAN POPLAR APHID GALLS
. The Canadian Entomologist 109 (3): 321-328. [should help sort out some of the unidentified poplar galls]