Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.2-1.3 cm. Small, fringes checkered. Male forewing with costal fold. Uppersurface black with small white spots, the white submarginal and median spot-bands of the forewing somewhat parallel and forming an apparent "X", the spot bands on the hindwing parallel, the hindwing with a very small white postbasal spot. Undersurface of hindwing with interspersed white and reddish-brown bands.

One flight, mostly May in coastal ranges and low elevations, mid-June through mid-July at high elevation, mid-April to mid-July for southern California Pyrgus ruralis lagunae (Scott 1986). June to mid-July in the Rocky Mountain region, March to August elsewhere except April and May in southern California (Glassberg 2001). Early May to mid-July in Canada (Layberry et al. 1998). Mid-May to early July in the Rocky Mountain states (Ferris and Brown 1981). June to mid-July in northern California (Emmel and Emmel 1962; Shapiro 1977), early March to early September in Oregon and Washington (Pyle 2002), late March to mid-August in Oregon (Warren 2005), April to mid-July in British Columbia (Threatful 1988; Guppy and Shepard 2001).

Best determined by a combination of small size, dark uppersurface with white submarginal and median spot bands forming an "X" on the forewing, the uppersurface of the hindwing with a small white postbasal spot; undersurface of hindwing with interspersed white and reddish-brown bands.

Non-migratory.

Wet and dry montane meadows, forest clearings, hillsides, roadsides, creek and river margins, above treeline in alpine terrain (Emmel and Emmel 1962; Shapiro 1977; Ferris and Brown 1981; Scott 1986; Threatful 1988; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001; Pyle 2002; Warren 2005). Habitat in Montana not described but probably similer.

Larval food plants are members of the Rosaceae including Fragaria and Potentilla (multiple species), possibly Geum and Horkelia, members of the Malvaceae including Sidalcea, in captivity members of the Ericaceae including Vaccinium (Ferris and Brown 1981; Scott 1986, 2006; Layberry et al. 1998; Guppy and Shepard 2001; Pyle 2002; James and Nunnallee 2011). Adults feed on flower nectar (including Dentaria, Fragaria, Potentilla, Taraxacum) and mud (Pyle 2002; Warren 2005; James and Nunnallee 2011; Scott 2014).

Females lay eggs singly on the undersides of host plant leaves (Scott 1986; James and Nunnalee 2011). Eggs hatch in 3-4 days (depending on temperature), develop from L1 instar to L5 instar and pupae in 32 days (low elevation cohorts) to 55 days (high elevation cohorts), depending on temperature for both cohorts. Overwinter as pupae, adults eclose (emerge from pupae) in about 62 days following exposure to warm spring temperatures. Larvae feed on host plant leaves, build silk-tied tube nests of host plant leaves, may cannibalize smaller larvae, pupate in late summer-early autumn in heavily silk-lined L5 instar nest (James and Nunnallee 2011). Males patrol or perch near the ground throughout the day in valley bottoms and grassy swales in search of or awaiting passing females (Scott 1975b, 1986; Warren 2005).