Message From Mary Beth Prondzinksi

Stanley A. Gorodenski stan_gorodenski at
Mon Oct 6 01:40:26 EDT 2003

Mary Beth wanted me to post the following message in Leps-L

Mary Beth Prondzinski

----- Forwarded Message -----
From: mbpi at
Date: Sat, 4 Oct 2003 08:24:59 -0500
Subject: Re:  Question on Vanessa cardui...
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Hello everyone!

Remember me?!  It's been awhile since I was on this listserv, but
something has come up that I would like your professional input on...

Here in the Midwest, and more specifically the Chicago, Illinois area
where I am, there was a HUGE irruption of Painted Ladies (Vanessa cardui)
which was first observed on the 18th of September.  All the individuals
observed were fresh and unblemished...indicating they were new emergents
as opposed to "migrants."

So here is my question:  Do Painted Ladies ever "reverse migrate"?  I
never observed any directional movement in the massive numbers, but
rather saw them flitting around from one nectar source to another without
exhibiting any territorial behavior.  These large numbers seemed to be a
phenomenon restricted to the middle regions of the US, including
Minnesota, Wisconsin, Iowa, Illinois, Kansas, etc. at least from the
variety of "sightings" that were reported.

Most interestingly...there was no observable movement of massive numbers
of Vanessas during the spring...rather, we had an unusually blustery,
cold spring with predominating northeasterly winds, right up until June
21st, when BAM...summer quite suddenly convened (!)  Few butterflies were
even seen until mid-summer, and even then numbers were modest, with the
dominating species being Monarchs, and a good representation of Hackberry
butterflies (including the rare-in-these-parts Snout butterfly).  But I
digress...  The Vanessas were a small handful, at best.

So what promoted this astounding irruption?!  The only clue I received
was an email of a photo of a Vanessa cardui caterpillar munching on an
unidentified Salix species.  Not much help considering the vast number of
host plants that Painted Ladies lay their eggs on (!)

Anyone of you experts want to posit a feasible conjecture on what
happened and why?!  I would greatly appreciate some knowledgeable
feedback, as I've been asked to write a "personal observation" on the
irruption for Chicago Wilderness magazine, and from the inquiries I've
made here in Chicago, there hasn't been one really GOOD explanation from
any of the local entemologists.  Granted, there is a dirth of "butterfly
experts" here, which is why I am enlisting your expertise!  

I might also add that after one week of Painted Ladies in my hair and in
my face...the temperatures dropped the point where the
observed intrepid few appeared to be "shell shocked" from the abrupt
wintery change. 

Thanks in advance for your much anticipated response!  Please cc: me if
you respond on LEPS-L, as I am no longer subscribed...

Mary Beth Prondzinski
mbpi at


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