Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.1-1.4 cm. Tailed, fringes unchecked. Uppersurface of male blue, female brown with blue at wing base, hindwing of both sexes with a few marginal black spots. Undersurface chalky-white with indistinct black spots (spots sometimes absent), a single reduced orange spot on hindwing margin at base of tail.

Several flights, March to April in southern California, late April to mid-August in most of west; one flight, late May to mid-July in north, mid-June through July in Arctic (Scott 1986). March/April to August, with partial second flight in southern lowlands (Glassberg 2001). First flight April to June, second partial flight in August in Rocky Mountain states (Ferris and Brown 1981). Late April to late August in Colorado (Emmel 1964; Scott and Scott 1978; Scott and Epstein 1987), late March to mid-September in Oregon and Washington (Pyle 2002), late April through July in Oregon (Warren 2005), late April to July in British Columbia (Threatful 1988; Guppy and Shepard 2001).

Best determined by presence of tail, uppersurface bluish, undersurface chalky-white with indistinct black spots (spots sometimes absent), a single reduced orange spot on hindwing margin at base of tail.

Non-migratory.

Undisturbed open areas, shrubsteppe, chaparral, foothill oak woodland, mesic montane meadows, streamsides, trailsides, above treeline in alpine fellfield (Emmel 1964; Shapiro 1977; Scott and Scott 1978; Scott 1986; Threatful 1988; Opler and Wright 1999; Glassberg 2001; Pyle 2002; Warren 2005); significantly more abundant in forest than grassland in northern Idaho (Pocewicz et al. 2009). In Glacier National Park, Montana reported from montane mesic meadows (Debinski 1993); in the Greater Yellowstone Ecosystem, reported from moist meadows, roadsides, sandy clearings, forest margins (Debinski and Pritchard 2002).

Larval food plants include Astragalus (several species), Lathyrus (several species), Lotus, Oxytropis, and Vicea (several species) (Scott 1986, 1992, 2006; Pyle 2002; Warren 2005). Adults feed on flower nectar (including Allium, Apocynum, Astragalus, Centaurea, Cerastium, Draba, Eriogonum, Lathyrus, Potentilla, Rhus, Sedum, Symphyotrichum, Taraxacum, Thlaspi, Trifolium, Vicea), horse manure, coyote dung, urine, and mud (Pyle 2002; Warren 2005; Scott 2014).

Females lay eggs singly on host plant flowers and young seed pods, sometimes in crack on stems near leaf base, up to 3 eggs on a single plant (Scott 1986, 1992, 2006; James and Nunnallee 2011). Number of eggs per ovariole (1/8 of total) about 80 (Ehrlich and Ehrlich 1978). Eggs hatch in about 4-5 days (depending on temperature), develop rapidly from L1 instar to mature L4 instar or pupae in about 14-25 days. Most larvae overwinter as mature L4 instar and delay pupation until exiting winter diapause. Adults eclose (emerge from pupae) in about 11-14 days (James and Nunnallee 2011). Larvae solitary, feed on host plant flowers and fruits, build no nest (but may be contained entirely within seed pod), cannibalistic when crowded, tended by ants (Conomyrma bicolor, Formica obscuripes, and Lasius niger in the wild, F. pilicornis reported in captivity), overwinter as mature L4 larvae (Scott 1979, 1986; Ballmer and Pratt 1991; James and Nunnallee 2011). Males perch and often patrol throughout the day in low depressions between shrubs, hillsides, at gully mouths, awaiting passing females (Scott 1975b, 1986).