Our species profile for this issue is the Moss’ Elfin, Incisalia mossii. The moss’s Elfin belongs to the group of butterflies we call hairstreaks, a subgroup of the large worldwide family Lycaenidae, which includes hairstreaks, blues, coppers and metalmarks. Many of the hairstreaks, as their name suggests, bear tail-like, or hair-like, extensions at the rear of their hindwings.  The group of hairstreaks we call elfins have no such “tails”, however, instead bearing a ” tomus” on their hindwing, a rounded globular extension to the wing projecting down in a direction perpendicular to the “tails” of other hairstreaks. Elfins are small, unobtrusive butterflies, adorned in camouflaged colors of browns and grays. All four of our elfins fly early in the spring, most species appearing in March, but the Moss’ Elfin is the earliest, with Washington records as early as late February. At higher elevations, mossii is found through late May.

Moss’ Elfin is a strictly western North American species, occurring in Washington, Oregon, northern California, the panhandle of Idaho and southern British Columbia, with some outlier populations in central Wyoming and northern Colorado. In Washington, mossii occurs mostly east of the Cascade Mountains, in a band along the eastern foothills extending from southern Okanogan to northern Klickitat counties, but it also occurs in a very spotty, broken distribution in the Olympic Mountains, other parts of Okanogan County, and in the Blue Mountains and Spokane County.

Moss’ Elfin is found in rocky areas where stonecrops, especially Sedum lanceolaturn, are found, typically in mid- to higher-elevation areas. Prime habitat is usually large flowery clearings with sagebrush and other shrubs, often adjacent to, but not in, forested areas.

All four of Washington’s elfin species hibernate through the winter in the chrysalis stage, enabling them to emerge early in the spring. The Moss’ Elfin can often be found flying while there are still patches of snow in the vicinity, and while their stonecrop (Sedum) host plants are barely emerging from the ground. After mating, the females lay their eggs singly on the stonecrop leaves. After hatching, the larvae feed on the stonecrop leaves and do not make nests. Larval color varies depending on foodplant, with ours usually pale greenish to greenish-brown, although bright pink individuals are found elsewhere. The larvae pupate approximately five weeks after the eggs are laid and, as the species is single brooded, the pupae hibernate through the summer, fall and winter to emerge early the following spring.

Dorsally the adults of all four of Washington’s elfins are mostly solid brown or reddish-brown. Because dorsal wings cannot easily be observed in the field, ventral wing markings are more useful for identification. Of our elfins the Western Pine Elfin is the most easily identified, by the dramatic dark brown zigzag lines on the underside of its hindwing. The Brown Elfin has a two-tone ventral hindwing, dark brown at the base and lighter brown on the outer half, with no white markings at all.

Our other two elfins, the Hoary and the Moss’, both have whitish (hoary) markings on the ventral hindwing, and are thus more likely to be confused. On the Hoary Elfin the entire outer half of the wing is hoary, but on mossii the white is limited to a mid-ventral hindwing band, or sometimes just a narrow white edging to a darker line across the middle of the ventral hindwing. Thus, the limited extent of the whitish markings on the ventral hindwing is the best diagnostic field mark to separate mossii from the Hoary Elfin. Further south in California, mossii is not always well marked with white and can be confused with the Brown Elfin, but here in Washington the identification is more straightforward.

The Moss’ Elfin is one of our most localized Washington species, being found in small, discrete colonies. Adults generally do not move very far from their place of emergence during their one­ week life span, and are never found far from their stonecrop foodplants. Adults readily take nectar from available flowers, and males engage in a “perch and wait” strategy for females. Moss’ Elfins are inconspicuous and easily overlooked. All elfins perch with their wings closed over their back, so dorsal wing surfaces can be observed only in the hand or in flight.

The Moss’ Elfin is always a welcome sighting, as it is generally scarce, not easily found and sought by butterfly enthusiasts, but most of all because it is a welcome harbinger of spring.

All photos by Dave Nunnallee

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