Euphydryas chalcedona hennei

Henne's Chalcedon (or Variable) Checkerspot

Euphydryas chalcedona hennei is a butterfly of the Colorado desert in San Diego and Riverside counties. The preferred host is the yellow-flowered Keckiella antirrhinoides var. microphylla (Scrophulariaceae). Generally this is a late spring, early summer flyer that can explode in numbers or (reportedly) not fly for years at a time during drought conditions. They may produce a second brood in the fall, and in autumn visits to Cactus Spring Trail from 2013 to 2016, I photographed at least one hennei each of the four years. Booms and busts aside, the norm is for larvae to feed in nests until about the third instar, then go into diapause until the plants recover in the spring. The transition from a ravenous post-diapausal larva to adult is rapid, perhaps only a few weeks.

James Scott named this subspecies in 1981 in Papilio (New Series) #1. The type locality is Box Canyon in San Diego County. The San Diego desert hennei are relatively dark in aspect, with a black ground color and cream/white and red markings on the dorsal side. As one gets up out of Anza-Borrego into the Cactus Springs Trail area, the phenotype lightens into what may be a blend zone with the lighter chalcedona corralensis populations in the deserts to the north. Gordon Pratt says these are "near corralensis" (pers. comm.). The nominate subspecies in, e.g., the San Gabriels is relatively darker in aspect than even hennei.