Photos of urban monarch overwintering sites California

[Paul Cherubini]

> You say "Šbut I have never seen any  evidence of butterfly killsŠ" by
> pesticide drift or accidental direct spray.  This is a casual
> observation and is far from being a definitive study that shows
> pesticides have no affect.  Thus, the question is still open.
 
People have seen and photographed monarchs clustering throughout the
winter on golf courses will little evidence of mortality from any factor save
the ocassional loss due to bird and yellow jacket predation. For example,
in the winter of 1995-96 monarch expert Dr. Dennis Frey at Cal Poly
San Luis Obispo observed that one of the two most stable and persistent
monarch colonies out of a dozen in his study area was located
on the Black Hill Golf Course in Morro Bay, Calif.
 
> The significant impact of pesticide and other chemical use may be on
> fertility and/or fecundity.  My question to you is:  Does drift and
> accidental spray from pesticides and other chemical applications affect
> the fertility and/or fecundity of the Monarch?
 
I've never heard of any insecticide that was known to substantially
reduce the fertility or fecundity of any lepidopteran due to
field exposures in the adult stage. The inventor of such a hypothetical
adult lep birth control chemical might potentially become an overnight
billionaire when you consider the practical potential applications
(e.g. gypsy moth control).
 
> I think an interesting study would be to tag Monarchs who
> overwinter in urban areas (such as parks, cemeteries, trees
> bordering golf courses,etc.) and  those who overwinter under
> natural conditions in the same geographic area
 
This has already been done to some extent.