Calephelis nemesis dammersi

Fatal Metalmark

Calephelis nemesis is a species found throughout Mexico and central America, and to the north into the southern U.S. from California to Texas. In southern California, we have subspecies dammersi. This is a multiple-brooded metalmark with at least two larval food plants: Baccharis salicifolia (mule fat), Baccharis glutinosa (Douglas' baccharis, salt marsh baccharis), and Encelia californica (bush sunflower, California brittlebrush, California encelia). This is a butterfly of the coastal mountains and foothills, in particular riparian or semi-riparian habitats where mule fat does well. The Santa Monica Mountains are a great place to look for it, but there are also records from the Palos Verdes Peninsula, the Gardena Willows Wetlands Preserve, parts of San Diego, and along the coast from Ventura to Santa Barbara; iNaturalist has plenty of helpful records. It's unclear to me whether this metalmark has a true diapause, and if so, what stage or stages are involved.

Calephelis nemesis - Fatal Metalmark
Calephelis nemesis dammersi - the fatal metalmark. From Malibu Creek State Park on April 17, 2009.
Calephelis nemesis - Fatal Metalmark
Another one from Malibu Creek State Park, a few years earlier. July 26, 2005.
Calephelis nemesis - Fatal Metalmark
The ventral side of Calephelis nemesis dammersi also has the "metalmarks". Same individual as immediately above.
Original description of Calephelis nemesis dammersi - Fatal Metalmark
Wilbur S. McAlpine named this butterfly in 1971 in the Journal of Research on the Lepidoptera. It's a little complicated, actually. McAlpine first named a distinctive population from Blythe dammersi. Then he gave the general (non-Blythe) California populations - which he found sufficiently different from the Arizona populations - the subspecific name californica. But it appears (and I'm not sure about this) that the Blythe population was just a summer form, and the earlier name, dammersi, applies to both.

©Dennis Walker