Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Laybery et al. 1998; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 2.5-2.6 cm in Rocky Mountain region. Large, forewing pointed. Overall coloration chocolate brown. Forewing crossed with brassy-gold spots, undersurface of hindwing with irregular metallic-silver band across disc.

One flight, mid-June to mid-July in the north, Rocky Mountains, Sierra Nevada; several flights, May to September in southern California and Northeast; nearly all year in Florida (Scott 1986). May to September, but April to November in southern Texas, southern Arizona, Pacific lowlands; June and July in North Dakota and Canada (Glassberg 2001). Early June to late July in Canada (Layberry et al. 1998). Late May to early August in Rocky Mountain states (Ferris and Brown 1981). Late May to early August in Colorado (Scott and Scott 1978; Scott and Epstein 1987), early May to late July in Nebraska (Johnson and Nixon 1967; Dankert and Nagel 1988), early June to mid-July in North Dakota (McCabe and Post 1976), early April to late August in Oregon and Washington (Pyle 2002), late April to early September in Oregon (Warren 2005), late May to early August in British Columbia (Guppy and Shepard 2001).

Combination of size, base color, and markings (forewing brassy-gold spots, undersurface of hindwing with metallic-silver band across disc) are unique.

Non-migratory.

Foothill canyons, prairie streamsides and roadsides, fields, gardens, urban parks (Ferris and Brown 1981; Scott 1986; Dankert and Nagel 1988; Opler and Wright 1999; Glassberg 2001; Pyle 2002; Giuliano et al. 2004; Warren 2005), generally avoiding disturbed sites and riparian areas dominated by exotic Tamarix (Hogsden and Hutchinson 2004; Nelson 2007; Nelson and Wydoski 2008). Habitat in Montana not described but probably similar.

Larval food plants are native and exotic members of the Fabaceae, including Acacia, Amorpha, Amphicarpa, Apios, Astragalus, Desmodium (several species), Gleditsia, Glycyrrhiza, Lathyrus, Lespedeza, Lotus (multiple species), Phaseolus (multiple species), Pueraria, Robinia (several species), and Wisteria (Ferris and Brown 1981; Scott 1986, 1992, 2006; Layberry et al. 1998; Guppy and Shepard 2001; Pyle 2002; Graves and Shapiro 2003; Warren 2005; James and Nunnallee 2011). Adults feed on flower nectar (including Ageratum, Allium, Amaryllis, Apocynum, Asclepias, Bidens, Blephilia, Buddleia, Cardamine, Carduus, Centaurea, Cephalanthus, Chrysanthemum, Cirsium, Consolida, Cornus, Cosmos, Dahlia, Delphinium, Dipsacus, Epilobium, Eupatorium, Geranium, Gilia, Glycyrrhiza, Hesperis, Hydrangea, Impatiens, Iris, Jamesia, Justicia, Lantana, Lavandula, Liatris, Lonicera, Lupinus, Lythrum, Medicago, Mentha, Monarda, Myosotis, Nepeta, Ocimum, Oenothera, Orbexilum, Origanum, Penstemon, Petunia, Phaseolus, Philadelphus, Phlox, Pycanthemum, Rhaphanus, Rudbeckia, Rubus, Scabiosa, Scutellaria, Silphium, Symphorycarpos, Tamarix, Thalictrum, Tilia, Tradescantia, Trifolium, Verbena, Veronia, Viola, Zinnia), dung, and mud (Venables and Barrows 1985; Bray 1994; Pyle 2002; Tooker at al. 2002; Giuliano et al. 2004; Warren 2005; Scott 2014).

Females lay eggs singly on undersurface of host plant leaves, usually top-most leaf of plant, rarely on uppersurface of leaf or stem, and rarely on nearby non-host plant (Scott 1986, 1992, 2006; James and Nunnallee 2011). Develop from egg hatch to L5 instar and pupae in about 30 days (mid-L3 to L5 instar and pupae in about 18 days), adults eclose (emerge) from non-diapause pupae in about 13-14 days, depending on temperature. Second broods overwinter as pupae (Scott 1979, 1986; James and Nunallee 2011). Larvae build silk-tied tubular leaf nest (larger with later instars), are solitary, feed on host plant leaves, leave nest at night to feed (Scott 1986, 1992, 2006; James and Nunnallee 2011). Males perch 1-2 m above ground throughout morning and early afternoon in gullies, woodland clearings, suburban yards, awaiting passing females (Scott 1975b, 1986).