Species Operophtera bruceata - Bruce Spanworm - Hodges#7437

7437

Winter Moth

wingspan 25-30 mm

larvae to about 20 mm

Adult: female has underdeveloped wings and does not fly; male forewing ground color grayish-brownish, generally darker than the similar (but larger and whiter) Autumnal Moth; terminal line a series of dark SINGLE dots -- a distinctive feature; dull yellowish scaling often present along costa; hindwing pale brownish-gray with small dark discal spot and indistinct lines [see "See Also" section below for distinguishing features of Autumnal Moth]

Larva: body bright green with 3 narrow yellowish-white stripes on each side; only 2 pairs of prolegs

coast to coast in southern Canada and northern United States

deciduous woods; females are found crawling on tree trunks and large branches; males fly low among trees, and are attracted to light

adults are active after leaves fall, from October to December

larvae in May and June

larvae feed preferentially on leaves of Sugar Maple, American Beech, and Trembling Aspen, but will also feed on willow and various other deciduous trees

one generation per year; overwinters as an egg which hatches in the spring; larvae eat leaves right down to the ribs in May & June, then pupate until October or November, when adults emerge; flightless females climb tree trunks and lay pale green eggs singly in bark cracks or on large branches; egg color changes to orange during winter

Autumnal Moth (Epirrita autumnata) forewing ground color is paler and usually more gray than brown; terminal line is a series of dark DOUBLE dots (not single dots as in the Bruce Spanworm); lacks dull yellowish scaling along costa (often present in Bruce Spanworm). Compare 4 images of both species at CBIF.

pinned adult images of 2 males, showing color variation (CBIF)

live adult & larva image plus other info (US Forest Service)

pinned adult image (Agriculture Canada)

images of all life stages plus description and biology (Canadian Forest Service)

live adult image (John Himmelman, Connecticut)