Common Least Skipper - Ancyloxypha numitor
[From Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001] Forewing 1.1-1.2 cm. Small, antennae short, wings rounded. Uppersurface of forewing primarly dark brown with coppery-orange apex and costa; hindwing yellow-orange with wide dark brown margin. Undersurface of forewing dark brown except pale orange apex and costa, hindwing unmarked pale orange.
Several flights northward, mid-June to early September; many flights in the south (Scott 1986). June to Septeber in the northern half of range, April to October in the southern half (Glassberg 2001). Mid-June to early September in Canada (Layberry et al. 1998), late June to September in the Rocky Mountain states (Ferris and Brown 1981), mid-June to early October in North Dakota (McCabe and Post 1976).
Best determined by a combination of small size, rounded wings, uppersurface of forewing primarly dark brown with coppery-orange apex and costa; hindwing yellow-orange with wide dark brown margin; undersurface of hindwing unmarked pale orange.
Southeastern Saskatchewan across southern Canada to Nova Scotia, south throughout the eastern US, in the west to southern Texas and eastern Mexico; scattered reports farther west (southern Alberta, southeastern Arizona) (Ferris and Brown 1981; Scott 1986; Layberry et al. 1998; Opler and Wright 1999; Glassberg 2001); 1067 m to 1676 m elevation in the Rocky Mountain states (Ferris and Brown 1981). In Montana, not reported through 1993 (Kohler 1980; Stanford and Opler 1993), but documented since 2003 in at least 16 eastern counties (FLMNH Lepidopterists' Society database), north to Roosevelt County and as far west as Sweet Grass County in the south; to 1220 m elevation. Locally rare to locally uncommon in the northern Great Plains (Glassberg 2001).
Wet grassy areas, ditches, marshes, slow-moving streams, open riparian areas (Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001), favoring less-disturbed grassland sites (Hogsden and Hutchinson 2004; Nelson 2007). Habitat in Montana not described but probably similar.
Larval food plants are typically tall wide-leaf grasses, including Agropyron, Bromus, Echinochloa, Leersia, Oryza, Panicum, Phalaris, Poa(?), Setaria, Spartina, Zea, and Zizaniopsis (Ferris and Brown 1981; Scott 1986, 1992, 2006; Layberry et al. 1998). Adults feed on flower nectar (including Alisma, Anemone, Asclepias, Boltonia, Cirsium, Erigeron, Eupatorium, Helianthus, Heliopsis, Houstonia, Lantana, Lindernia, Lobelia, Lotus, Lycopus, Lythrum, Medicago, Mentha, Oxalis, Phlox, Phyla, Potentilla, Prunella, Scutellaria, Stachys, Taraxacum, Trifolium, Verbena, Vicea, Viola) and mud (Tooker et al. 2002; Scott 2014).
Limited information. Females lay eggs singly on host plant leaves (both surfaces and on vertical leaves). Larvae eat host plant leaves, live in rolled-leaf nest (near leaf tip when L1 instar), diapause (hibernate) as L3 and L4 instar (possibly pupa), undergo 5 instars before pupation (Scott 1979, 1986, 1992, 2006; Layberry 1998). Males patrol weakly throughout the day among grasses at stream edges, springs, reservoirs, in search of females (Scott 1975b, 1986).
- Literature Cited AboveLegend: View Online Publication
- 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.
- Hogsden, K.L. and T.C. Hutchinson. 2004. Butterfly assemblages along a human disturbance gradient in Ontario, Canada. Canadian Journal of Zoology 82: 739-748.
- 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.
- McCabe, T.L. and R.L. Post. 1976. North Dakota butterfly calendar (including possible strays). Journal of Research on the Lepidoptera 15:93-99.
- Nelson, S.M. 2007. Butterflies (Papilionoidea and Hesperiodea) as potential ecological indicators of riparian quality in the semi-arid western United States. Ecological Indicators 7:469-480.
- 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. 1975b. Mate-locating behavior of western North American butterflies. Journal of Research on the Lepidoptera 14:1-40.
- 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.
- Scott, J.A. 1992. Hostplant records for butterflies and skippers (mostly from Colorado) 1959-1992, with new life histories and notes on oviposition, immatures, and ecology. Papilio new series #6. 185 p.
- Scott, J.A. 2006. Butterfly hostplant records, 1992-2005, with a treatise on the evolution of Erynnis, and a note on new terminology for mate-locating behavior. Papilio new series #14. 74 p.
- Scott, J.A. 2014. Lepidoptera of North America 13. Flower visitation by Colorado butterflies (40,615 records) with a review of the literature on pollination of Colorado plants and butterfly attraction (Lepidoptera: Hersperioidea and Papilionoidea). Contributions of the C.P. Gillette Museum of Arthopod Diversity. Fort Collins, CO: Colorado State University. 190 p.
- 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.
- Additional ReferencesLegend: View Online Publication
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- 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.
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