Sunday, September 18, 2011

Fall Cankerworm Moth

Fall Cankerworm Moth - Alsophila pometaria
A small drab moth.  I didn't think I'd be able to identify it without a lot of work and randomly searching through moth pictures.  But I stumbled upon its photograph in "Moths and Caterpillars of the North Woods" by Jim Sogaard while trying to identify a different moth.  When I saw the picture it made sense.  Cankerworms have been quite common at Westwood Hills Nature Center (where I found this moth and a few others) the past few springs.  Last year there were so many Cankerworm caterpillars that you would hear what sounded like rain falling in certain parts of the woods at Westwood.  The sound was all the frass (caterpillar poop) falling through the leaves.  Some trees appeared to be almost completely defoliated, but none seemed to suffer permanent damage.

The Fall Cankerworm overwinters as an egg, the caterpillar feeds in the spring, pupates, and the adult moth flies and mates in the fall, often in cold weather.  The similar (especially the caterpillar) Spring Cankerworm, Paleacrita vernata, feeds as a caterpillar in the spring, like the Fall Cankerworm, but drops to the ground and burrows, waiting until late winter to pupate.  The adult Spring Cankerworm flies in the early cold spring.  In both cases the females are flightless.