Apodemia mejicanus deserti

Desert Metalmark

The desert (or sonoran) metalmark, usually referred to as a subspecies of Apodemia mejicanus (and once lumped with mormo along with the rest of the complex), is found in both the Colorado and Mojave deserts. Adults can fly almost any time, largely depending on the quality of its preferred host, Eriogonum inflatum (desert trumpet), which in turn depends on precipitation. So they are said to be "facultatively multiple-brooded," meaning they may have several broods in a year if conditions allow, or you may not see them much in dry years. In some places, deserti in sympatric (i.e., found in the same place) - or nearly so - with some other member of the mormo complex, and genetic testing bolsters the idea that they are a separate species from, say, virgulti or any of the single-brooded "mormon metalmarks".

In an important American Butterflies article from the Summer/Fall/Winter 2011 issue, Gordon Pratt, John Emmel and Gary Bernard placed the various mormo-complex populations in groups: mejicanus (including our deserti); duryi; virgulti; and mormo. These groups are defined by brood number and timing, egg size, and larval food plants. In the mejicanus group, only deserti is in southern California.

Deserti was named by Barnes and McDunnough in 1918 based on specimens from "Mr. G. Field of San Diego who captured them on July 11th in La Puerta Valley, S. Calif.; we have similar specimens from Palm Springs, Riverside Co., Calif., on the borders of the Mohave Desert." It took a little research to find La Puerta Valley, which I could not find on any maps I have. Turns out, an expert on small mammals named Frank Stephens (who, I believe, lived in La Puerta Valley, and whose field notes from collecting trips in the southwest are available online) collected some golphers on Mason's Ranch, described in the 1913 publication mentioning these golphers as being "five miles west of Vallecito, on the old overland (Butterfield) stage road." Mason's Ranch is also said to be "located at the lower end of La Puerta Valley." Mason Valley - indeed at the lower end of a large valley - is along the S2, with much of it just outside the jagged boundaries of Anza-Borrego Desert State Park. So La Puerta Valley is approximately 5-7 miles due south of Scissors Crossing, and a similar distance east of Lake Cuyamaca. It is where one would go to enter Oriflamme Canyon up the Mason Valley Truck Trail. Mason Valley/Vallecito are still extant and sparsely inhabited, but the name "La Puerta Valley" has seemingly all but faded away. All that to say: the type locality for deserti is this particular valley in the Anza-Borrego area.

Apodemia mejicanus deserti - Desert Metalmark
Apodemia deserti - the desert metalmark. I found these flying in good numbers in a patch of their host Eriogonum inflatum at a turnout along Highway 74 in Palm Desert. June 9, 2019.
Apodemia mejicanus deserti - Desert Metalmark
Sometimes these are called Apodemia mejicanus deserti. This is from Rock Corral, San Bernardino Co., April 14, 2008.
Apodemia mejicanus deserti - Desert Metalmark
This one was patrolling a wash in the Kingston Range, where the host E. inflatum was common. April 13, 2020.
Apodemia mejicanus deserti - Desert Metalmark
Across the border in Nevada, at Cottonwood Pass, I found this deserti taking nectar. April 22, 2020.
Apodemia mejicanus deserti - Desert Metalmark
This female was ovipositing on the buds of the host inflatum along highway 74 south of Palm Desert. June 8, 2019.
Egg of Apodemia mejicanus deserti - Desert Metalmark
And here's the best shot I could get of the resulting egg. June 8, 2019.
Caterpillar of Apodemia mejicanus deserti - Desert Metalmark
This larva was on Eriogonum inflatum in the Lost Palms wash in southern Joshua Tree National Park, directly north of Chiriaco Summit. May 20, 2020.
Caterpillar of Apodemia mejicanus deserti - Desert Metalmark
Probably a last instar, feeding on the stem of desert trumpet. This was at Rattlesnake Canyon in Johnson Valley, August 30th, 2023.
Chrysalis of Apodemia mejicanus deserti - Desert Metalmark
A pupa found within the stalk of Eriogonum inflatum. This was at a turnout above Palm Desert. October 29, 2019.
description of Apodemia (mejicanus) deserti - Desert Metalmark
The original description of this butterfly, from 1918. It was named by William Barnes and J.H. McDunnough in Contributions to the Natural History of the Lepidoptera of North America, vol.4, part 2, p.75, with an illustration on plate XII. My personal opinion is that the advent of photography in these journals led to some unfortunate illustrations. Some of the hand-drawn illustrations in the old journals were truly beautiful, and also - perhaps ironically - clear for the reader compared to photographs. It's interesting that the very best illustrations are often in the oldest volumes; typography too in many instances.

©Dennis Walker