Hormaphis cornu (Shimer, 1867)

Hamamelistes cornu Shimer, 1867.
Hormaphis hamamelidis Osten-Sacken, 1861 [secondary homonym of Hamamelidis Fitch 1851].
Hormaphis hamamelidis (Fitch): Walsh, 1867; Pergande, 1901; von Dohlen and Gill, 1989 [misidentifications].
Hormaphis hamamelidis Osten-Sacken: Thomas, 1877 [misidentification].
Pemphigus hamamelidis (Fitch): Thomas, 1877 [misidentification].

Alate virginoparae depart from galls in June and migrate to river birch to produce the first aleurodiform generation on the undersides of leaves. Two more aleurodiform generations follow; the last produces sexuparous nymphs. Mature sexuparae depart from leaves of river birch and fly back to witch-hazel in mid-September to early October and deposit sexual nymphs.

Summary: Hormaphis hamamelidis forms small, conical galls usually without basal constriction, is autoecious on witch-hazel, and lives at high elevations in northern regions of the eastern United States. Hormaphis cornu forms larger, conical galls that are usually constricted at the base, is host-alternating between witch-hazel and river birch, and is found at low elevations in the mid-Atlantic and southern regions of the eastern United States.

Range: VA, DC