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Montana Field Guides

Juvenal's Duskywing - Erynnis juvenalis


Global Rank: G5
State Rank: SNR

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General Description
[From Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001] Forewing 1.8-1.9 cm. Large. Uppersurface of male blackish-brown with scattered long whitish hairs on forewing, female paler brown and mottled with more definite pattern of alternating dark and gray spot rows, both sexes with a series of white postmedian spots on forewing, hindwing with scattered tawny spots, a white fringe on southwestern subspecies, brown fringe elsewhere. Undersurface with two round pale subapical spots near leading edge of hindwing.

Phenology
One flight, mid-April through May in northeastern US, June in Saskatchewan, mid-May through June in Ontario, mid-February to early April in Florida; multiple flights in Arizona, April to early September (Scott 1986). Mid-March through August in Arizona, April through June elsewhere (Glassberg 2001). Early May to late June in Canada (Layberry et al. 1998). Mid-May through June in Rocky Mountain states (Ferris and Brown 1981). Mid-May to early June in north-central Nebraska (Dankert and Nagel 1988), mid-May to late June in North Dakota (McCabe and Post 1976).

Diagnostic Characteristics
Best determined by large size and dark-brown to paler brown color, both sexes with a series of white postmedian spots on uppersurface of forewing, undersurface of hindwing with two round pale subapical spots near leading edge.

Species Range
Montana Range

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Range Comments
Isolated in central Arizona south to central Mexico; also across southern Canada from Saskatchewan east to Nova Scotia, south throughout eastern US as far west as western North Dakota, northeastern Wyoming and adjacent South Dakota (Black Hills), eastern Nebraska, eastern Oklahoma, western and central Texas (Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001). In Montana not reported through 1993 (Kohler 1980; Stanford and Opler 1993); first documented in 2003 from Carter County at 1103 m elevation (FLMNH Lepidopterists' Society database), near Alzada and the only stands of native oaks in the state. Rare to uncommon in Arizona, locally rare in western Texas, common in eastern Texas, locally uncommon in the Dakotas and Saskatchewan (Glassberg 2001).

Migration
Non-migratory.

Habitat
Oak woodlands and thickets, oak-juniper woodland, oak-pine woodland, riparian woodlands, along woodland trails, creekbeds, riverbanks (Ferris and Brown 1981; Scott 1986; Dankert and Nagel 1988; Opler and Wright 1999; Glassberg 2001). Habitat in Montana not described but probably similar; documented only in the single county (Carter) with native oak (Quercus macrocarpa).

Food Habits
Larval food plants are tree and shrub members of the Fagaceae, especially Quercus (many species), possibly Fagus americana (Kendall 1966; Ferris and Brown 1981; Scott 1986; Layberry et al. 1998). Adults feed on flower nectar (including Antennaria, Astragalus, Bidens, Cephalanthus, Cercis, Clematis, Coreopsis, Cornus, Delphinium, Erigeron, Erythronium, Fragaria, Linaria, Lithospermum, Lobelia, Malus, Mertensia, Nepeta, Orbexilum, Polymonium, Prunus, Pycnanthemum, Ranunculus, Rubus, Staphylea, Trifolium, Verbena, Verbesina, Vibernum, Viola), dung, and mud (Kendall 1966; Macior 1975; Scott 1986; Tooker et al. 2002; Wall et al. 2003).

Reproductive Characteristics
Females lay eggs singly on or near host plant seedlings and young leaves (Kendall 1966; Scott 1986); a captive female laid 32 eggs in one day (Kendall 1966). Eggs hatch in about 8-9 days, larvae feed on leaves, live in rolled leaf nests, typically develop slowly over several months, mature larvae overwinter (enter diapause), pupate in spring, adults eclose (emerge from pupae) in about 30-45 days depending on temperature (Kendall 1966; Scott 1979, 1986). Males perch on vegetation (especially host plant) 1-4 m above ground in forest margins waiting for passing females (Scott 1986; Layberry et al. 1998).

References
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Citation for data on this website:
Juvenal's Duskywing — Erynnis juvenalis.  Montana Field Guide.  .  Retrieved on , from