Perhaps we should change the common name to "The Formerly-Common Sooty Wing," since this little glossy-black butterfly with a white "face" is now teetering on the edge of regional extinction. On our transect, it was formerly found at all the low-elevation sites but as of 2005 was still present only in West Sacramento. As recently as a decade before this was a "junk species," breeding in vegetable gardens and vacant lots on weedy Pigweeds (genus Amaranthus) and occasionally on the closely-related Cockscomb in flower gardens. There are plenty of hosts around - perhaps more than ever - but P. catullus has disappeared. The fat, apple-green larva with a black head and cervical shield was easily located in its rolled-leaf nest.
Multiple broods, March-October. Males "fly a beat" along roadsides with a very characteristic zigzag flight near the ground. Both sexes visit low flowers such as Lippia and Heliotrope and, in lawns, clovers and small yellow-flowered Oxalis.
The collapse of this species and of the Large Marble (Euchloe ausonides) leaves butterfly biologists absolutely baffled. What is going on?