Euphydryas chalcedona hennei

Henne's Chalcedon (or Variable) Checkerspot

Euphydryas chalcedona hennei is a butterfly of the Colorado desert. It can be common or even abundant on Cactus Spring Trail south of Palm Desert, a trail with plenty of the preferred host, 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. Checkerspots depend on the quality of their host plants, which is in turn dependent on rainfall, so their larvae have the ability to go into diapause if need be until good plant material is available. Then again, 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.

Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot
Euphydryas chalcedona hennei on Cactus Springs Trail, Santa Rosa Wilderness, March 31, 2011.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot
'Henne's' Variable Checkerspot. Hellhole Canyon in Anza-Borrego Desert State Park, January 30, 2006. This sighting was an early record for California.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot
Euphydryas chalcedona hennei, also on Cactus Springs Trail, March 23, 2010. These can be extremely common along this trail in the spring.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot
A ventral of 'Henne's' Variable Checkerspot on Cactus Springs Trail, Santa Rosa Wilderness, May 14, 2006. Chris Henne was one of our great southern California lepidopterists; several butterflies have been named after him.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot larvae
Larval nest with lots of Henne's Variable Checkerspot caterpillars on Desert Bushpenstemon. Cactus Spring Trail, Santa Rosa Wilderness, May 30, 2010.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot larvae
A closer view of larvae, these a little further along. This checkerspot can be abundant on this trail in the spring, and I had often wondered what the host plant or plants were at this location; on this hike I found out, as larval nests were easily found.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot larvae
Last instar larva of Euphydryas chalcedona hennei, same trail as above, April 15, 2011.
Euphydryas chalcedona hennei - 'Henne's' Variable Checkerspot pupa
On March 3, 2017, I found this chalcedona caterpillar attached to a yucca leaf on Cactus Spring Trail close to Horsethief Creek. My next visit was March 30th, and the butterfly had emerged, leaving behind this pupal skin.
Original description of Euphydryas chalcedona hennei - 'Henne's' Chalcedon Checkerspot description
James Scott named ssp. hennei in his journal Papilio (New Series) 1:4 in 1981. There had been confusion with the name quino, which proved to apply to an editha subspecies, while Gunder (in a 1932 paper) had used the name hennei for an aberrant form of what was then considered Euphydryas chalcedona quino. So as I understand it, Scott was able to substitute the name hennei for quino because Gunder's formulation didn't conform to the rules. The name hennei was "unavailable" ("[A] scientific name that does not conform to Articles 10 to 20, or that is an excluded name under Article 1.3."), so he could use it for the desert chalcedona subspecies formerly known as quino.

©Dennis Walker