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Archive for November 7, 2013

Bruce Spanworms Emerging & Mating

11-7-13 winter moth IMG_4880I try not to repeat post topics, but in the past two days the sudden emergence of inch-long, tan moths in the woods has been so dramatic that I couldn’t not mention them. These ghost-like, light tan moths are referred to by entomologists as Bruce Spanworm moths, Operophtera bruceata, named after an entomologist by the name of Mr. Bruce. They are often called Winter Moths, due to the fact that they are one of the latest moths to be seen flying, as well as Hunter Moths, as they share the woods with hunters at this time of year. From October to December Bruce Spanworm moths emerge, mate and lay eggs. While this timing is unusual, it makes sense when you think about it — many birds, their primary predators, have left for their wintering grounds. All the moths you see in the air are males — females are wingless and cannot fly. The females crawl up the trunk or branch of a tree and send out pheromones to attract winged males. After mating, the female lays eggs which hatch in the spring, and the larvae feed on a wide variety of deciduous leaves, favoring Trembling Aspens, Sugar Maples, American Beeches and willows. Periodic outbreaks of these caterpillars can result in heavy defoliation.

NB: “This is easily confused with Operophtera brumata – Winter Moth, which is an introduced species from Europe and an abundant pest in the Northeast. Also easily confused with Autumnal Moth (Epirrita autumnata).” Kent McFarland