Hormaphidini
Guides
Hamamelistes
Spiny Witch-Hazel Gall Aphid (for H. spinosus), Birch Blister Aphid (for H. betulinus)
Hamamelistes is a genus of gall-forming aphids in the tribe Hormaphidini, distributed disjunctly in eastern North America and Eurasia. Species in this genus induce pouch galls on host plants in the family Hamamelidaceae, particularly witch-hazel (Hamamelis spp.). Most species have host-alternating life cycles involving Hamamelis and birch (Betula spp.), though at least one species is presumed monoecious. The genus includes three described species: H. betulinus, H. cristafoliae, and H. spinosus, plus the recently described H. blackmani.