California tortoiseshells

[Harobed99 at aol.com]

Hi Leps Listers,
    This weekend, driving along a ridge-top dirt road in Yolo County, I came 
across thousands of California Tortoiseshells (Nymphalis californica) flying 
and nectaring.  When driving through two days earlier, there was no sign of 
them.  I read in the Audobon Society Field Guide to North American 
Butterflies, that "the California Tortoiseshell may be rare or absent from 
large parts of its range for several years.  These dearths are followed by 
periods of enormous abundance, involving emigrations over immense areas, 
which seem to be related to population pressures, host plant availability, 
and climate conditions."  
    It was quite an amazing phenomenon to witness.  I was just wondering if 
anyone could give me any more information about them. There seem to be 
reports of explosions of several species this year...Painted Lady's, Red 
Admirals, CA Tortoiseshells.  
    Thanks,
    Deborah

 
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