Vanessa and the white dot

[Michael Gochfeld]

Will Cook's photos are really very interesting and sobering.  Glassberg also
emphasizes the "bold black median FW band" on V. cardui
as well as the absence of the white spot.

I find that more often than not, I see the ventral surface of nectaring
"ladies" in which case the two large ocelli on the ventral hindwing of
V. virginiensis stands out compared with the four smaller spots of V.
cardui.   I have often seen V. virginiensis where the white spot was not
visible due to wear, but I've never seen a cardui with the white spot, so
this is an interesting aberration, pointing out the importance of getting a
good enough look to see a combination of characters.   H.F. Nijhout used V.
cardui as one of his experimental subjects reported in his book "The
Development and Evolution of Butterfly Wing Patterns".
Interestingly he showed that cold shock produced alterations in the 4 spot
pattern and that individuals without the four ventral eyespots could be
produced experimentally.

It would be interesting to know how often the white spot appears in cardui,
particularly in those areas where thousands are reported (we don't seen
thousands in a whole year here (NJ).

Mike Gochfeld

Will Cook wrote:

> Several field guides (e.g., Glassberg) and other sources (e.g.,
> http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/bflyusa.htm)
> mention that one way to tell American Lady (Vanessa virginiensis) from
> Painted Lady (Vanessa cardui) is the presence of a small white spot in
> the orange field below the black apical patch in American Lady.
>
> However, on 11/11/01 I found a Painted Lady with a white dot - this is
> apparently not reliable field mark.  I just posted a photo of this
> Painted Lady at http://www.duke.edu/~cwcook/pix/paintedlady.html (second
> photo).
>
> --
> Charles W. "Will" Cook                  w 919-660-7423
> http://www.duke.edu/~cwcook            cwcook at duke.edu
> Box 90340, Biology Dept., Duke Univ., Durham, NC 27708
>
>
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