Message From Mary Beth Prondzinksi

Robert Dana robert.dana at
Mon Oct 6 12:01:17 EDT 2003

Regarding Mary Beth's report of the appearance of large numbers of V.
cardui in Chicago on Sept. 18:

Here in Minneapolis the irruption began about Sept. 10. We had a
protracted summer drought here with warmer than average temperatures.
Our first heavy rainfall in a number of weeks occurred the evening of
the 11th continuing into the 12th. There has been some speculation that
the emergence was triggered by the rain, with the large numbers being
the result of an accumulated pool of aestivating pupae. I am sceptical
of this hypothesis, but maybe others reading this can offer some
support. Even after several nights of freezing temps here there are
still butterflies around, nectaring or basking. I have seen no courtship
behavior or mating pairs. When the butterflies first appeared I noted a
behavior I hadn't ever seen in Vanessa before: individuals soaring with
horizontally fixed wings, riding small thermals upwards until I couldn't
see them any more.

I used to have the URL of a web site that took reports of Vanessa
observations and compiled them on a map--but I have lost it. Can anyone
provide this?

Robert Dana, Ph.D.
Natural Heritage and Nongame Research Program
500 Lafayette Rd, Box 25
St. Paul, MN 55155
651 297-2367
Email: robert.dana at


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