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Montana Field Guides

Pacuvius Duskywing - Erynnis pacuvius


Global Rank: G5
State Rank: S5

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General Description
[From Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.6-1.7 cm (larger in second flight). Small, males lack tibial tufts on hindlegs. Uppersurface variable, uniform dark brown without white forewing apical spots to highly mottled blackish-brown with gray scaling, black patches and white spots on outer half of forewing; hindwing lighter brown with white fringe (nominate subspecies) or dark brown fringe (California and Pacific Northwest). Undersurface lighter brown, hindwing may show a submarginal row of pale spots.

Phenology
One flight in the north, May through June, June through July at high elevation; several flights in the south, April through September (Scott 1986). May to mid-July in one brood areas, March to October in two-brood areas (Glassberg 2001). June and July in Canada (Layberry et al. 1998), early May to early August in Colorado (Scott and Scott 1978; Scott and Epstein 1987), late April to late July in Oregon and Washington (Pyle 2002), early May to early August in Oregon (Warren 2005), early May to mid-July in British Columbia (Guppy and Shepard 2001).

Diagnostic Characteristics
Best determined in Montana by a combination of size, absence of male tibial tufts, uppersurface highly mottled blackish-brown with gray scaling, black patches and white spots on outer half of forewing; hindwing lighter brown with dark brown fringe. Undersurface lighter brown, hindwing may show a submarginal row of pale spots.

Species Range
Montana Range

Click the legend blocks above to view individual ranges.
 


Range Comments
Southern British Columbia south through the Cascades and Sierra Nevada to northern Baja California, south in the Rocky Mountains from western Montana, Colorado to central Mexico (Scott 1986; Opler and Wright 1999; Glassberg 2001); up to about 2743 m elevation in the Rocky Mountain states (Ferris and Brown 1981), 1951 m to 2865 m elevation in Colorado (Scott and Scott 1978), 30 m to at least 2499 m elevation in Oregon (Warren 2005). In Montana, reported from at least 11 counties, mostly western but as far east as Yellowstone County (Kohler 1980; Stanford and Opler 1993; FLMNH Lepidopterists' Society database), mostly < 1525 m elevation. Rare to uncommon (Glassberg 2001).

Migration
Non-migratory.

Habitat
Chaparral, open conifer (ponderosa pine/Douglas fir) woodland, open deciduous woodland, shrubland, roadside ditches, riverbanks, montane clear-cuts (Brown 1957; Scott and Scott 1978; Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Warren 2005). Habitat in Montana not described but probably similar.

Food Habits
Larval food plants are members of the Rhamnaceae, and include several species of Ceanothus (Brown 1957; Ferris and Brown 1981; Scott 1986, 1992, 2006; Layberry et al. 1998; Guppy andf Shepard 2001; Warren 2005; James and Nunnallee 2011). Adults feed on flower nectar (including Antennaria, Apocynum, Arctostaphylos, Astragalus, Ceanothus, Cerastium, Erysimum, Geranium, Hedysarum, Heterotheca, Jamesia, Lesquerella, Mertensia, Sedum, Senecio, Symphoricarpos, Taraxacum, Thlaspi) and mud (James and Nunnallee 2011; Scott 2014).

Reproductive Characteristics
Limited information. Females lay eggs singly on upper surface of small, new-growth host plant leaves, usually the basal half (Scott 1992; 2006; James and Nunnallee 2011). Eggs hatch in about 7 days, develop from L1 instar to L5 instar and pupation 38 days in captivity, but L5 instar typically overwinters (hibernates), adults eclose (emerge from pupae) in about 14 days in captivity (Scott 2006; James and Nunnallee 2011). Larvae solitary, build silk-tied tubular leaf nest, feed on host plant leaves, feed nocturnally, overwinter as L5 instar, pupate in final nest (Scott 2006; James and Nunnallee 2011). Males perch on hilltop rocks, vegetation < 1 m above ground throughout the day, patrol around host plants even on hillsides, awaiting passing females or actively seeking them (Scott 1975b, 1982, 1986; Warren 2005).

References
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Citation for data on this website:
Pacuvius Duskywing — Erynnis pacuvius.  Montana Field Guide.  .  Retrieved on , from