What feature is shared between the adult male Winter Moth and the adult male Bruce Spanworm?

Both species have wingless females.

When assessing defoliation sources, distinguishing between the Winter Moth (*Operophtera brumata*) and the Bruce Spanworm (*Operophtera bruceata*) is necessary, and the shared physical characteristics are informative. According to the comparison table, while the males differ slightly in specific coloration (Winter Moth males are pale brown/grey, Spanworm males are brownish-grey), a key morphological similarity exists in the female reproductive structure. Specifically, the females of both the Winter Moth and the Bruce Spanworm are described as being wingless. This feature ensures that once the male moths mate with them during the late fall flight, egg laying must occur immediately near the site of mating, as the females cannot disperse widely.