Females are flightless, with tiny but well-formed wings. Males: wings variable in coloration: whitish gray, brown, or black. Melanics are common, and always have veins darker than base color of the wing.
The PM line is gently sinuous and relatively smooth, especially compared with the jerky PM line of denticulata. The smooth shape of the PM line is the best feature to distinguish this moth at a glance, coupled with a slightly larger size and greater tendency to hold the wings more outstretched when at rest. The other phigalias almost always hold their wings together so the hindwing is covered. The median line is more isolated from the The PM line than in the other phigalias.
Distribution pattern: Eastern.
Reilly pers obs
These moths emerge in late winter and early spring. See photograph of 1st instar larva on a boxelder bud
Rindge FH. 1975. A revision of the new world Bistonini (Lepidoptera Geometridae). Bulletin of the American Museum of Natural History 156(2): 71-155.
McGuffin WC. 1977. Guide to the Geometridae of Canada (Lepidoptera) II. Subfamily Ennominae. 2. Memoirs of the Entomological Society of Canada 101: 1-125.
Covell CV. 1984. A field guide to the moths of Eastern North America. Houghton Mifflin Company: Boston. 496 pp.