Painted Lady Migration?

Ernest Williams ewilliam at
Mon Mar 16 08:58:01 EST 1998

Painted ladies are known for outbreaks and large movements, and one theory
is that their abundance in the western U.S. is determined partially by El
Nino.  After a year of heavy southwestern rains, the vegetation is lush,
and painted lady numbers consequently go up the next summer.  This pattern
was first pointed out by M.T. Myres (1985, Can Field-Nat. 99:147).  In a
talk at the annual meeting of the Lepidopterists' Society at Yale last
July, Scott Kocher, a former student of mine, and I gave evidence that
supported this pattern, and we predicted that 1998 would be a big year for
painted ladies because a big El Nino had been predicted for this past fall
and winter.  The El Nino obviously came to pass.  Ann Swengel (1993, Am.
Butterflies 1(2)) also commented on Myres' pattern and cautioned,
correctly, that other factors interact with El Nino events to affect
painted lady abundance.  By its size, this El Nino may be the big
determinant this year.  We'll find out this summer how big an outbreak
there is of painted ladies.

Ernest Williams, Dept. Biology, Hamilton College, Clinton, NY

>I spent a couple of hours today at friend's house in Walnut Creek, California.
>It was a nice sunny 70 F day and I noticed a sparse but steady stream of
>Painted Ladies headed from south to north. The rate was about one every
>5 minutes. They all seemed to be on a mission to fly as far as possible in one
>day. This reminded me of the big migration back in the 1980's. 
>Has anyone else noticed a migration underway?
>Chuck Vaughn  <aa6g at>

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