Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.3-1.5 cm. A tiny sulphur. Uppersurface black and yellow, forewing with broadly black forewing tips and black bar along inner margin; female with more extensive black; hindwing with some orange infused. Undersurface of forewing with orange or yellow basal patch and black submarginal spots, hindwing of summer form pale yellow, winter form olive-green.

Many flights, March to December in the south where adults overwinter, becoming more common northward only in summer (Scott 1986). Early May to early December in Colorado (Brown 1957; Emmel 1964; Scott and Scott 1978), late June in northern California (Shapiro 1993), late July in Washington (Pyle 2002), early July to late September in Montana (FLMNH Lepidopterists' Society database).

Best determined by a combination of tiny size, yellow uppersurface with broad black forewing tips, undersurface of forewing with orange or yellow basal patch and black submarginal spots, hindwing olive-green.

Migratory, although populations in the southeastern US (Florida, Georgia) are non-migratory; resident across southern US, moves long distances northward but does not return southward (Nabokov 1953; Clench 1976; Scott 1986; Shapiro 1993; Glassberg 2001; Pyle 2002).

Dry meadows, desert, thorn scrub, weedy fields, prairies, road edges, hillsides, open woodland, parks and gardens, along irrigation ditches, abandoned agricultural fields, sometimes at high elevations (Emmel 1964; Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002). Habitat in Montana not described but probably similar; most records from large river riparian corridors (FLMNH Lepidopterists' Society database).

Larval food plants include mostly native and exotic species of composites, such as Bahia, Bidens (multiple species), Cosmos, Dyssodia, Helenium, Hymenothrix, Palafoxia, Tagates, and Thelesperma, possibly non-composites such as Erodium, Galium, Mollugo, and Stellaria (Ferris and Brown 1981; Scott 1986, 1992, 2006; Graves and Shapiro 2003; James and Nunnallee 2011). Adults feed on flower nectar (including Achillea, Bidens, Cerastium, Chrysanthemum, Chrysothamnus, Coreopsis, Erigeron, Euphorbia, Geranium, Gutierrezia, Heterotheca, Heliopsis, Machaeranthera, Medicago, Oxalis, Pectis, Phyla, Sedum, Solidago, Symphyotrichum, Taraxacum, Tribulus, Trifolium, Verbena, Viola) and mud (Tooker et al. 2002; James and Nunnallee 2011; Scott 2014).

Females lay eggs singly usually on the uppersurface of leaves of host plant seedlings, rarely on sepals (Scott 1986, 1992, 2006; James and Nunnallee 2011). Larvae develop from L1 to L4 instar and pupae in about 23 days, adults eclose (emerge from pupae) in another 15 days (about 38 days after egg-hatch), depending on temperature (James and Nunnalee 2011). Larvae build no nest, feed at night, cause "window-paning" of leaf when L1 instar, consume leaves and flower petals from edges as older instars, usually pupate horizontally on underside of leaf or vertically on stem of host plant; apparently no stage hibernates or undergoes diapause (Scott 1979, 1986; James and Nunnallee 2011). Males patrol throughout the day low to the ground in flats and other low areas in search of females (Scott 1975b, 1986; James and Nunnallee 2011).