butterflies, clouds, and wind

John Fleckenstein JFMM490 at wadnr.gov
Wed Mar 10 18:23:42 EST 1999


I think response to clouds varies by species.  On midwestern prairies, I could be watching abundant skipper activity.  Passage of a cumulous cloud with a small, 5 acre shadow would cause most of the skippers to vanish.  The fritillaries, whites, and company would still be active.  When the cloud passed, the skippers reappeared.  I wonder if the disapperance was due to physiology or behavior.  While that seemed to happen even on hot days, as someone else mentioned, temperature is often important.  There, and in the Pacific Northwest, I see far more activity on a hot cloudy day than a cool, cloudy day.

In the Pacific Northwest, spring weather is usually cool and wet.  We have a number of species that fly in May.  That's a very tough time for a solar powered animal to make a living on the wet side of the Cascades.  We can go two or three weeks with little or no sunshine, but the species hang on.  Sometimes  they manage to do quite well.  In May 1996, we did a transect survey at a Euphydryas editha taylori site and found about 500 individuals.  We were impressed with the count, especially since it was 55 degrees and drizzling during the survey.  I don't think we saw more then two individuals flying.  The rest were perched.  I guess they emerge and hang around, waiting for good flying weather.  I'm sure there are advantages to flying in May, but they escape me.  The evolutionary risk of flying in May seems higher than the possible advantages.  It's partially stimulating, partially depressing to see such an obvious anamoly and not have the reason be equally obvious.

John Fleckenstein, zoologist
Washington Natural Heritage Program
Department of Natural Resources
(360) 902-1674
John.Fleckenstein at wadnr.gov



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