California Tortoiseshell - Not a Painted Lady!
Painted and West Coast Ladies are not the only butterflies in the western United States to be undergoing an outbreak. California Tortoiseshells have also been present to abundant in some places in northern California and Oregon where Painted Ladies probably have not yet arrived in any large numbers. They look like this: https://bugguide.net/node/view/1447798. While they are interesting butterflies in their own right, and worthy of further study, they are not Painted Ladies, so please be careful not to confuse the two when reporting Painted Lady sightings. Also, according to a March 18 posting on DesertLeps, California Tortoiseshells have also become abundant in the area of southern California around the Santa Rosa and San Jacinto Mountains National Monument, replacing the Painted Ladies, which are surprisingly not that common there now and seem to have mostly departed the area. However, Painted Ladies were still abundant in southern California on March 16 near the Mescal Range in San Bernardino County, CA, about 138 miles (222 km) to the north-northeast; no California Tortoiseshells were observed there.
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BTW, in good years, California tortoiseshells engage in mass migrations like the painted ladies in California do, but are not as abundant or as widely distributed.
PS: You say "surprisingly not all that common now." Surely the change in numbers is evidence that the adults migrated north en masse. I haven't checked the maps, but here is an iNat report of mass migration on 3/6 at Coachella Valley National Wildlife Refuge in the CA desert. Observer said: "There were hundreds & of these all flying WNW in the span of about 10 minutes." See https://www.inaturalist.org/observations/21016915
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