What's the derivation of the word "Xerces"?

 

The Xerces Blue butterfly (Glaucopsyche xerces) is perhaps the most famous of the extinct United States butterflies. It was a fascinating species that was once locally common at suitable habitats on the San Francisco Peninsula. It was of great interest to lepidopterists due to the remarkable variation in wing pattern; indeed, some of these varieties were originally considered to represent distinct species, until it was observed that the various forms readily interbred. The Xerces Blue, in essence, was a species which consisted of only one population, although great variation was present in the individuals comprising the population. From this standpoint alone, the butterfly would have made an excellent subject for genetic, evolutionary, and ecological studies.

Xerces was a small butterfly, the upper wing surfaces iridescent blue-violet in the male, brown in the female. Populations inhabited stabilized sandy sites with rather low-growing vegetation, including the former Lone Mountain Cemetery, the Presidio military base (just west of the Naval Hospital and north of Lobos Creek), several locations in the Sunset District (including the western slopes of Twin Peaks), and the Lake Merced area. By the 1930's, the butterfly was restricted to vacant lots. The last known specimens were taken March 23, 1941 by W.H. Lange at the Presidio.

The Xerces Blue flew generally from mid-March to mid-April. Females laid their eggs on several leguminous plants: Deerweed (Lotus scoparius), Yellow-flowering Beach Lupine (Lupinus arboreus), and a blue-flowering lupine species (possibly Lupinus micranthus). Apparently, Deerweed was the most commonly utilized and preferred caterpillar food. All of the above foodplants are much more widespread than was the Xerces Blue: Deerweed, for example, occurs throughout the California coastal foothills. Close relatives of the Xerces Blue utilize Deerweed and various lupine species at many locations in the western United States. It appears that geographic isolation and climate, rather than foodplant specialization, limited Xerces to the San Francisco Peninsula. The French entomologist Boisduval named the butterfly for the Persion king Xerxes (486 - 465 B.C.), but used the French spelling, Xerces.

Return to top