Interesting. California Tortoiseshells have been mentioned frequently, over the past year, on the NWLeps list serve. It's been been an irruption period, with millions of adults migrating into Washington last year. As far as I can tell, it's prime time for new county records for this species because it's more abundant and widespread than it has been in a long time. Larval food plants for California Tortoiseshells are various species of wild lilac (ceanothus spp.). I don't know how widespread and abundant the various wild lilacs are in western Washington but, based on the bright condition of some of the California Tortoiseshells I've seen in Capitol Forest, there must be some Ceanothus in the Thurston County area somewhere. So, the huge number of California Tortoiseshells that migrated to Washington in 2006 appear to have laid eggs which overwintered as caterpillars and have now emerged (in 2007) as adult butterflies. Some of the adult butterflies that migrated here in 2006 survived into 2007 as well. I'm just not sure how long they live and whether those that survived the winter as flighted adults are still flying, like those over the snow on Mount Rainier. I'd be curious is anyone knows these kinds of details.

Kelly McAllister
Olympia, Washington
----- Original Message -----
From: Richard Isherwood
To: Tweeters
Sent: Friday, July 20, 2007 11:00 AM
Subject: [Tweeters] Butterflies in the Snow


This is a bit off subject, but may be of some interest.

On a recent climb of Mt Rainier we were surprised to see literally hundreds of butterflies near the summit, flying to and fro over the snow with no obvious consistent direction.There was no food source for them anywhere nearby.We took a photo from which I think they were California Tortoiseshells. My butterfly book tells me that these breed in the montane vegetation zone of the Cascades and they do have spectacular population booms and mass migrations. This seemed to be a mass suicide mission.

I wonder if anyone else has seen anything similar.

Richard Isherwood
Port Townsend Wa
Rjisherwood at gmail.com






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