This species is a medium-sized gray to translucent butterfly in the large and diverse family Nymphalidae. This family, collectively known as the brush-foots, is characterized by the front pair of legs being reduced to thin, brush-like appendages with fused tarsi that are held tightly beneath the thorax.
Oeneis is a relatively small genus of dull-colored butterflies generally occurring in arctic-alpine habitat where their striated and marbled undersides camouflage them against rock, lichen, and bark.
In the Pacific Northwest, Oeneis melissa is distinct from other Oeneis species by the smoky-gray (rather than golden- or reddish-brown) dorsal wing color. Oeneis melissa beanii is the only subspecies of O. melissa that occurs in Cascadia. In both the males and females of this subspecies, the dorsal wings and ventral forewing are smoky-gray and thinly scaled, almost to the point of transparency. Eyespots are usually absent in this species, although faint, small eyespots on the dorsal wings occur infrequently in some females. The ventral hindwing is mottled (heavily peppered with black on a background of whitish-gray). Ventral hindwing mottling varies with subspecies; in O. m. beanii, the mottling is either uniform or with a vague, darker median band with a white edge. This band is less distinct than is seen in other subspecies The ventral hindwing usually has a row of small spots near the wing margin. The rounded hindwings are usually larger in area than the more drawn-out forewings, and the wing fringes on both wings are checkered. The wing span of this species is 4.2 to 5.1 cm (1 5/8 to 2 in.). There are no similar species with which O. melissa could be confused in Cascadia.
The gray-white eggs of this species are subconical, with the base flattened and rounded, and about 20 vertical ribs. The first instar larvae are pale greenish white with two very short, stubby tails. The dorsal, subdorsal, and lateral lines are pale brown, the underside is dull white, and the feet and legs are translucent whitish. Mature larvae have a grey green dorsal line, and dark spots edged with white lines between segments; below this, the ground color is grey buff with blackish longitudinal streaks and two brown dorsolateral lines. The lateral band is broad and deep black and has a light buff line below. The spiracular band is dark grey, the underside, legs, and prolegs are grey buff, and the head is green yellow with a brown tint.
Pupae of this species (from Colorado) are colored as follows: the thorax and back of the head are green-yellow with a brownish tint; the undersides of the head and wings are black brown; the abdomen has alternating bands of yellow and brown grey with each of the grey bands finely edged in carmine; and the spiracular band is tinged with carmine. Due to difficulty securing and rearing Oeneis melissa, this species was the only Washington butterfly not included in James and Nunnallee’s 2011 book on the life histories of Cascadia butterflies. Illustrations of the larva and pupa of this species are provided in Scott.