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Juvenal's Duskywing - Erynnis juvenalis
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
Range Descriptions
Native
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).
Stewardship Responsibility
References
- Literature Cited AboveLegend:
View Online Publication
Dankert, N.E. and H.G. Nagel. 1988. Butterflies of the Niobrara Valley Preserve, Nebraska. Transactions of the Nebraska Academy of Sciences 16:17-30.- Ferris, C.D. and F.M. Brown (eds). 1981. Butterflies of the Rocky Mountains. Univ. of Oklahoma Press. Norman. 442 pp.
- Glassberg, J. 2001. Butterflies through Binoculars: A Field Guide to the Butterflies of Western North America. Oxford University Press.
- Kendall, R.O. 1966. Larval food plants for five Texas Hesperiidae. Journal of the Lepidopterists' Society. 20(1):35-41
- Kohler, S. 1980. Checklist of Montana Butterflies (Rhopalocera). Journal of the Lepidopterists' Society 34(1): 1-19.
- Layberry, R.A., P.W. Hall, and J.D. LaFontaine. 1998. The Butterflies of Canada. University of Toronto Press. 280 pp. + color plates.
- Macior, L.M. 1975. The pollination ecology of Delphinium tricorne (Ranunculaceae). American Journal of Botany 62:1009-1016.
- McCabe, T.L. and R.L. Post. 1976. North Dakota butterfly calendar (including possible strays). Journal of Research on the Lepidoptera 15:93-99.
- Opler, P.A. and A.B. Wright. 1999. A field guide to western butterflies. Second edition. Peterson Field Guides. Houghton Mifflin Company, Boston, Massachusetts. 540 pp.
- Scott, J.A. 1979. Hibernal diapause of North American Papilionoidea and Hesperioidea. Journal of Research on the Lepidoptera 18(3): 171-200.
- Scott, J.A. 1986. The butterflies of North America: a natural history and field guide. Stanford University Press, Stanford, California.
- Stanford, R.E. and P.A. Opler. 1993. Atlas of western USA butterflies: including adjacent parts of Canada and Mexico. Unpubl. Report. Denver and Fort Collins, Colorado 275 pp.
- Tooker, J.F., P.F. Reagel, and L.M. Hanks. 2002. Nectar sources of day-flying lepidoptera of central Illinois. Annals of the Entomological Society of America 95(1): 84-96.
- Wall, M.A., M. Timmerman-Erskine, and R.S. Boyd. 2003. Conservation impact of climatic variability on pollination of the federally endangered plant, Clematis socialis (Ranunculaceae). Southeastern Naturalist 2:11-24.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Allen, T.J., J.P. Brock, and J. Glassberg. 2005. Caterpillars in the field and garden: a field guide to the butterfly caterpillars of North America. Oxford University Press.
- Brock, J.P. and K. Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Houghton Mifflin Company, New York, NY 284 pp.
- Forister, M.L., C.A. Halsch, C.C. Nice, J.A. Fordyce, T.E. Dilts, J.C. Oliver, K.L. Prudic, A.M. Shapiro, J.K. Wilson, J. Glassberg. 2021. Fewer butterflies seen by community scientists across the warming and drying landscapes of the American West. Science 371:1042-1045.
- Forister, M.L., E.M. Grames, C.A. Halsch, K.J. Burls, C.F. Carroll, K.L. Bell, J.P. Jahner, et al. 2023. Assessing risk for butterflies in the context of climate change, demographic uncertainty, and heterogeneous data sources. Ecological Monographs 93(3):e1584. https://doi.org/10.1002/ecm.1584
- Johnson, K. and E. S. Nixon. 1967. The Rhopalocera of northwestern Nebraska. American Midland Naturalist 78:508-528.
- Reinthal, W.J. 1966. Butterfly aggregations. Journal of Research on the Lepidoptera 5:51-59.
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