Other Common Names
Winter Moth (not to be confused with the true
Winter Moth, O. brumata, Hodges #7436)
Synonyms and other taxonomic changes
Operophtera bruceata (Hulst, 1886)
Cheimatobia bruceata Hulst, 1886
Operophtera bruceata occidentalis Troubridge & Fitzpatrick, 1993 (Hulst, 1896)
Explanation of Names
Operophtera bruceata occidentalis (Hulst, 1896) was listed in the 1983 MONA checklist as a full species, synonymized as a subspecies of Operophtera bruceata (Hulst, 1886) in Troubridge & Fitzpatrick (1993), and considered worthy of full species status in Gwiazdowski et al. (2013).
Identification
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]
Comparison of Operophtera brumata and O. bruceata, uncus is shown, the scales have been brushed off the tail of the abdomen.
Larva: body bright green with 3 narrow yellowish-white stripes on each side; only 2 pairs of prolegs
Range
coast to coast in southern Canada and northern United States
Habitat
deciduous woods; females are found crawling on tree trunks and large branches; males fly low among trees, and are attracted to light
Season
adults are active after leaves fall, from October to December
larvae in May and June
Food
larvae feed preferentially on leaves of Sugar Maple, American Beech, and Trembling Aspen, but will also feed on willow and various other deciduous trees
Life Cycle
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
See Also
Winter Moth (
Operophtera brumata), an invasive species from Europe, now a major pest in the northeastern and northwestern US
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.
Fall Cankerworm females are also wingless, and adults fly during the same times as
O. bruceata.
Print References
Gwiazdowski, R.A., J.S. Elkinton, J.R. Dewaard, M. Sremac, 2013.
Phylogeographic Diversity of the Winter Moths Operophtera brumata and O. bruceata (Lepidoptera: Geometridae) in Europe and North America. Annals of the Entomological Society of America. 106 (2):
143-151.
Internet References
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)
