cardui and thistles

[Kondla, Norbert FOR:EX]

There is published evidence of very high population densities on the
Canadian prairies. Certainly my observations over many years are that
thistles are certainly far less abundant in natural habitats vs
agriculatural fields and other areas disturbed by human activity. See:
Byers, J.R., B.T. Roth, R.D. Thomson and A.K. Topinka. 1984. Contamination
of mustard and canola seed by frass of painted lady caterpillars, Vanessa
cardui (Lepidoptera: Nymphalidae). The Canadian Entomologist 116:1431-1432.

-----Original Message-----
From: Erik Runquist [mailto:erunquist at hotmail.com]
Sent: Monday, February 25, 2002 4:16 PM
To: leps-l at lists.yale.edu
Subject: cardui and thistles


Has anyone, or does anybody know of any theories about how the spread of 
exotic thistles has affected cardui immigrations? I suspect that ladies are 
generally able to reach higher population densities (and reach farther 
north) than pre-colonization times because of these pervasive weeds.  I 
realize that this is a largely untestable hypothesis, but here I almost 
exclusively find caterpillars on bull and Canada thistles.
Just curious...
Erik Runquist
Ashland, OR


_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com


 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl 
 

 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl