Compton Tortoiseshell
Nymphalis vau-album
Description 2 1/2-2 7/8" (64-73 mm). Broad, ragged wings. Above, rich rust-brown at base, blending into yellow-gold crescents near margin, with heavy black spotting on FW; HW costa has 1 big black spot bordered on outside edge by frost-white patch. Beneath, various shades of gray, brown, and tan, striated and dotted, usually darker on inner half. Pale blue-gray crescents often line outer margin; small silver "V" or comma mark in HW cell below. FW trailing edge straight.
Similar Species Anglewings are smaller and narrow-winged, with more ragged borders, and lack white spot above; trailing FW margin concave (not straight). California Tortoiseshell is smaller, lighter, and less spotted; lacks silver "V".
Life Cycle Eggs laid in clusters. Caterpillar pale green, chartreuse-speckled with branched black spines; feeds communally on birches (Betula), willows (Salix), and perhaps poplars (Populus). Brown chrysalis angled, with horned head; often hangs from wood. Overwintering adults
lay eggs in spring for new brood in June or July.
Flight 1 brood; any month.
Habitat Clearings and tracks in dense deciduous woodlands; also canyons and rivercourses.
Range Subarctic Alaska and Canada south to Oregon, Colorado, Minnesota, and mountains of Missouri and North Carolina.
Discussion The "vau-album" of the scientific name refers to the whitish-silver "V" below, which places this butterfly close to the anglewings, although in every other respect it is clearly a tortoiseshell. It is occasionally numerous when conditions are right, clustering around fallen fruit, sap, or wet earth. But this big butterfly is notorious for its unpredictability; for years at a time it may be absent from a given district.
Source
