Saturday, January 18, 2014

Fall Cankerworms





Male and female Fall Cankwerworms
 
    It may not look like it, but both insects pictured are the same species. They are Fall Cankerworms, Alsophila pometaria, and in this species, the females are wingless. This is one of the very few moths who remain active through winter, at least during warmer days. These Geometrid (inchworm) moths mature this late in the year and thus avoid many potential predators.
    The females of course cannot fly, sacrificing wings in order to be able to commit more resources to egg production. They send out pheromones to attract the winged males and then lay their eggs in cracks and crevices in trees. The emerging caterpillars "balloon" in the spring by sending silk out to be carried by the wind to the various trees and shrubs they feed on.
    There are many other unusual characteristics to this moth: how females produce genetic copies of themselves some seasons, how the variable caterpillars are usually light green when in low numbers but almost black when there are many, and other traits, but we will return to talk about these during the summer when we find their larvae.    
    For now, if you find a moth out and about this time of year, there's a good chance it's a Fall Cankerworm. I actually tried to move the female over and see if I could act as match-maker, but the female apparently was not sending out any pheromones.
 

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