Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Layberry 1998; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.3-1.5 cm. Uppersurface tawny-orange and blended into wide dark borders, male forewing stigma with black interior fuzz; females variable, tawny-orange to very dark. Undersurface of hindwing greenish with irregular silvery-white chevron (postmedian band), chevron spots often edged in dark brown or black, the most basal spot offset inward giving posterior arm a 3-step appearance.

One flight, usually mid-June to mid-July; June to early July at low elevation, late June to early August at high elevation (Scott 1986). May to early September, less at any single locality (Glassberg 2001). June to August in Canada (Layberry et al. 1998). Late May through July in the Rocky Mountain states (Ferris and Brown 1981). Late may to mid-August in Colorado (Emmel 1964; Scott and Scott 1978), early June to early September in North Dakota (McCabe and Post 1976), late June to mid-July at higher elevation in northern California (Emmel and Emmel 1962; Shapiro 1977), early May to late July in Oregon and Washington (Pyle 2002), late May to early July in Oregon (Warren 2005), mid-May to mid-June in British Columbia (Guppy and Shepard 2001).

Best determined by a combination of uppersurface tawny-orange and blended into wide dark borders, undersurface of hindwing greenish with irregular silvery-white chevron (postmedian band), chevron spots often edged in dark brown or black, the most basal spot offset inward giving posterior arm a 3-step appearance.

Non-migratory.

Sagebrush steppe, prairie, aspen parkland, dry montane meadows and summits, sometimes above treeline in alpine grassland and ridges (Emmel and Emmel 1962; Emmel 1964; Shapiro 1977; Scott and Scott 1978; Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001; Warren 2005). Habitat in Montana not described but probably similar.

Larval food plants are grasses, including Achnatherum, Bouteloua, Elymus, Festuca, Koeleria, rarely Danthonia, Poa (Emmel et al. 1970; Ferris and Brown 1981; Scott 1986, 1992; Warren 2005); also Bromus, Cynodon, Setaria in captivity (James and Nunnallee 2011). Adults feed on flower nectar (including Arnica, Asclepias, Astragalus, Cryptantha, Erigeron, Eriogonum, Erysimum, Geranium, Harbouria, Oxytropis, Penstemon, Sedum, Senecio) and mud (Scott 2014).

Females lay eggs singly on underside of host plant leaves or near host plant (Scott 1986, 1992), on host plant stems or inflorescences in captivity (James and Nunnallee 2011). Eggs hatch in about 9 days, depending on temperature, L1 instar wanders before settling, produces slight silking when at rest but no nest through L2 instar, develop to L4 instar in 42-51 days, construct silked tubular leaf nests on ground as L3-L4 instars, rarely feed and move outside nest as L4 instar, overwinter as L3 or L4 instars, resume activity in spring, build new leaf nests, develop to L5 instar and pupate in cocoon within nest near base of host plant in about 23 days (Scott 1979; Pyle 2002; James and Nunnallee 2011). Males perch throughout the day on hilltops, ridge crests, sometimes fence lines, awaiting passing females (Scott 1975b, 1986; Warren 2005; James and Nunnallee 2011).