Acmon Blue

Plebejus acmon

Lepidoptera: Lycaenidae

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Nabokov Theory on Butterfly Evolution Is Vindicated

Characteristics: Male--dorsal wing predominantly iridescent blue; female--predominately brown. Marginal orange markings on dorsal hindwing on both sexes. Metallic scales are present around the black spots. These spots are arranged in a row adjacent to the ventral hindwing margin. The presence of these metallic scales (often rubbed off in worn specimens) is one characteristic distinguishing the genus Plebejus from Shijimiaeoides (an exception in Orange County; Plebejus icarioides). Forewing length: 1014 mm.

Similar Species: Shijimiaeoides battoides bernardino is somewhat similar but smaller. Male bernardino lacks orange on the dorsal hindwing, and there are no metallic scales on the ventral hindwing of bernardino specimens.

Habitats, Behavior: Adults are often found on Wild Buckwheat flowers, but may nectar on a wide variety of other blossoms. The species is occasionally found "puddling" at streams and seeps.

Distribution: The Acmon Blue is usually found wherever Eriogonum fasciculatum (Wild Buckwheat) grows. Records are generally from the lowland areas and canyons of the Santa Ana Mountains. The Acmon Blue is rarely found at high elevations in the Santa Ana Mountains.

Flight Period: Multiple brooded, flying from late February or March, to October. The spring and early summer broods are often the largest.

Larval Foodplants: Emmel and Emmel (1973) list Lotus scoparius as the principal foodplant in southern California, although Astragalus and Eriogonum (wild buckwheat) are also utilized. In the lowlands of Orange County, particularly along the coast and at Villa Park Dam, I feel Eriogonum fasciculatum is the primary foodplant. A prostrate Lotus sp. seems to be utilized at Yaeger Mesa (upper Trabuco Canyon).

Other Remarks: This species is usually common where found. Until at least 1970, an isolated but thriving colony existed on an isolated stand of buckwheat in a sandy area near the Santa Ana River in Orange (near the intersection of Batavia and Taft Avenues). However, the development of an equestrian center has destroyed most of this relict clump of native vegetation. Early spring females in the lowlands have extensive blue scaling on the dorsal wing and are referred to as form "cottlei". Later brood females are usually brown on the dorsal wing with no evidence of blue. At higher elevations the Santa Ana Mountains, form "cottlei" has been taken into mid July. These specimens may represent the first brood at these high elevations.

Further Information: Goodpasture (1973; 1974) is the latest and most exhaustive treatment of the taxonomy, biology, and food plant preferences of acmon and related species.

From Orsak, L. J. (1977). The Butterflies of Orange County, California. Center for Pathobiology Miscellaneous Publication #3. University of California Press, New York. 349pp.

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