Bruce Spanwing Moth

A couple of days ago we saw a pale moth flying across the garden – late November, snow on the ground, temperatures around zero or below – and shrugged as it flew away. This morning we got a closer look at it, or a relative.

I am reasonably confident that it is a Bruce Spanwing Moth (Operophtera bruceata) and that November is, indeed, their flight season. Also known as the hunter’s moth, or native winter moth

There are several Operophtera species and one that is visually very similar is the “Winter Moth” which is found here but is actually from Europe originally. The critical field mark, according to my references, is the little, dark tick mark (uncus) on the wing shown in the picture below.

This must be a male as the females have undeveloped wings and cannot fly.

As to the ID, confidently given above, it seems that Bruce spanworm is known to hybridize with winter moth.The two species look almost identical to one another; however, they can be distinguished morphologically by comparing uncus shape or by using DNA analyses. Bruce spanworm uses the same pheromone as winter moth which probably leads to this miscegenation.

The caterpillars feed on maple and other deciduous tree buds in spring before falling the ground and pupating in the soil with adults emerging at the start of winter.

A new species for me and for the garden list. Fascinating stuff.