Update: During the week of April 11, 5 more migrating Painted Ladies have been observed at various locations, all going N. There thus appears to be a migration afoot, but a minimal one!
Update: On March 12, 2011 at 11:54 AM, a Painted Lady in migratory mode, flying rapidly from SE to NW about 6' off the ground, was observed at Suisun City, Solano County--the first record this year known to me. It was small and pale, of the migratory desert phenotype.
I’ve begun receiving inquiries about whether or not to expect a Painted Lady (Vanessa cardui) migration this spring. In good years they would already be showing up, but there have been no reports so far anywhere in California, to my knowledge. The phenomenon depends on breeding success in the desert wintering grounds, which in turn depends on the rains producing a good crop of annuals for the larvae to feed on. After good late autumn and December rains, the tap was turned off for seven weeks—just like here—and the early annuals either dried up or froze. There were good rains over the President’s Day weekend—almost 2 inches at Anza-Borrego—which have already triggered another round of germination. But is it too little, too late? It all depends on March. 1992 had a very wet March after a dry midwinter. However, the northward migration is controlled by photoperiod (we think), and any butterflies that are around in March will head north rather than try to breed down south. So the timing is dicey. As of now, I would NOT expect a big flight here this spring.
To keep apprised of conditions:
If there is a good bloom going there is at least a chance of a butterfly outbreak; if an outbreak occurs it is generally noted on the updates. Good luck! PS: The Sacramento Bee tries to maintain a wildflower update site at http://www.sacbee.com/wildflowers
, and several local and county Chambers of Commerce do the same.