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Montana Field Guide

Montana Field Guides

Silvery Blue - Glaucopsyche lygdamus

Native Species

Global Rank: G5
State Rank: S5

Agency Status


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General Description
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.3-1.6 cm. Uppersurface of both wings with black margin and white unchecked fringe; male bright iridescent sliver-blue, female dark brown with or without blue basally. Undersurface off-white to gray-brown, forewing with single postmedian row of round and white-edged black spots, hindwing spots as large as on forewing to nearly absent, no marginal or submarginal spots on either wing.

One flight; February to mid-May in California, mid-May to mid-July at higher elevation and in the north (Scott 1986). May through June in much of western range, late June through August at high elevation and in Alberta and Saskatchewan, February to April in California (Glassberg 2001). Mid-March to early September in Oregon and Washington (Pyle 2002), late March to mid-August in Oregon (Warren 2005), late April to mid-August in southeastern British Columbia (Threatful 1988).

Diagnostic Characteristics
Best determined by a combination of the uppersurface of both wings with black margin and white unchecked fringe; undersurface off-white to gray-brown, forewing with single postmedian row of round and white-edged black spots, hindwing spots as large as on forewing to nearly absent, no marginal or submarginal spots on either wing.

Species Range
Montana Range Range Descriptions


Range Comments
Alaska south to Baja California and central New Mexico, east across boreal Canada to Quebec, Labrador, Newfoundland, south in the east through the Great Lakes Region and Appalachian Mountains to northern Alabama and Georgia (Scott 1986; Opler and Wright 1999; Glassberg 2001); 1676 m to 3230 m elevation in Colorado (Brown 1957; Scott and Scott 1978; Ferris and Brown 1981), 122 m to at least 2743 m elevation in Oregon (Warren 2005), 456 m to 1829 m elevation in southeastern British Columbia (Threatful 1988). In Montana reported throughout the state (Kohler 1980; Stanford and Opler 1993). Locally uncommon to common (Glassberg 2001).

Observations in Montana Natural Heritage Program Database
Number of Observations: 60

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


Open sites, pasture, grasslands, foothills, montane meadows, bogs, banks of watercourses, avalanche chutes, above treeline in alpine seeps and tundra (Scott 1986; Threatful 1988; Opler and Wright 1999; Glassberg 2001; Pyle 2002). In Glacier National Park, Montana reported from xeric and mesic montane meadows (Debinski 1993), in the Greater Yellowstone Ecosystem reported in wet to xeric montane meadows (Debonski et al 2013).

Food Habits
Larval food plants include Astragalus (multiple species), Hedysarum, Lathyrus (multiple species), Lotus, Lupinus (multiple species), Medicago, Melilotus, Oxytropis, Thermopsis, and Vicea (multiple species) (Scott 1986, 1992, 2006; Pyle 2002; Warren 2005; James and Nunnallee 2011). Adults feed on flower nectar (including Allium, Astragalus, Barbarea, Berberis, Cerastium, Erigeron, Eriogonum, Erysimum, Hymenopappus, Hymenoxys, Harbouria, Iris, Lepidium, Lesquerella, Linum, Lonicera, Medicago, Melilotus, Mertensia, Oxytropis, Phacelia, Physaria, Senecio, Thermopsis, Thlaspi), bird droppings, mammal dung, and mud (Pyle 2002; Warren 2005; Scott 2014).

Reproductive Characteristics
Females lay eggs singly on host plant flower buds, sometimes immature leaves (Scott 1986, 1992, 2006; James and Nunnallee 2011). Number of eggs per ovariole (1/8 of total) about 40 (Ehrlich and Ehrlich 1978). Eggs hatch in 4-6 days (depending on temperature), reach L2 instar in 3-4 days, reach L4 (or L5) instar and pupate 20-21 days (perhaps as much as 26 days) after oviposition, larvae wander off host plant to pupate at plant base, pupal stage overwinters (hibernates) up to 10 months (Scott 1979; Guppy and Shepard 2001; James and Nunnallee 2011). Larvae solitary, feed on flowers, leaves, fruits, do not build nests, are tended by ants (Formica, Myrmecocystus, Taponima) in the wild and captivity (Scott 1986; Ballmer and Pratt 1991; Warren 2005; James and Nunnallee 2011).

  • Literature Cited AboveLegend:   View Online Publication
    • Ballmer, G.R. and G.F. Pratt. 1991. Quantification of ant attendance (myrmecophily) of lycaenid larvae. Journal of Research on the Lepidoptera 30(1-2): 95-112.
    • Brown, F.M. 1957. Colorado Butterflies. Proceedings; Numbers Three through Seven. Denver Museum of Natural History, Denver, Co.
    • Debinski, D. 1993. Butterflies of Glacier National Park, Montana. Occasional Papers of the Museum of Natural History, the University of Kansas, Lawrence, Kansas. No. 159: 1-13.
    • Debinski, D.M., J.C. Caruthers, D. Cook, J. Crowley, and H. Wickham. 2013. Gradient-based habitat affinities predict species vulnerability to drought. Ecology 94(5): 1036-1045.
    • Ehrlich, A.H. and P.R. Ehrlich. 1978. Reproductive strategies in the butterflies: I. Mating frequency, plugging, and egg number. Journal of the Kansas Entomological Society 51(4): 666-697.
    • 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.
    • Guppy, C.S. and J.H. Shepard. 2001. Butterflies of British Columbia: including western Alberta, southern Yukon, the Alaska Panhandle, Washington, northern Oregon, northern Idaho, northwestern Montana. UBC Press (Vancouver, BC) and Royal British Columbia Museum (Victoria, BC). 414 pp.
    • James, D.G. and D. Nunnallee. 2011. Life histories of Cascadia butterflies. Corvallis, OR: Oregon State University Press. 447 p.
    • Kohler, S. 1980. Checklist of Montana Butterflies (Rhopalocera). Journal of the Lepidopterists' Society 34(1): 1-19.
    • 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.
    • Pyle, R.M. 2002. The butterflies of Cascadia: a field guide to all the species of Washington, Oregon, and surrounding territories. Seattle Audubon Society, Seattle, Washington. 420 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.
    • 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.
    • Scott, J.A. and G.R. Scott. 1978. Ecology and distribution of the butterflies of southern central Colorado. Journal of Research on the Lepidoptera 17(2): 73-128.
    • 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.
    • Threatful, D.L. 1988. A list of the butterflies and skippers of Mount Revelstoke and Glacier National Parks, British Columbia, Canada (Lepidoptera). Journal of Research on the Lepidoptera 27(3-4): 213-221.
    • Warren, A.D. 2005. Lepidoptera of North America 6: Butterflies of Oregon, their taxonomy, distribution, and biology. Contributions of the C. P. Gillette Museum of Arthropod Diversity, Colorado State University. Fort Collins, Colorado. 406 pp.
  • 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.
    • Caruthers, J.C., and D. Debinski. 2006. Montane meadow butterfly species distributions in the Greater Yellowstone Ecosystem. University of Wyoming National Park Service Research Center Annual Report, 2006. Vol. 30, Art. 14. 85-96.
    • Debinski, D.M., R.E. VanNimwegen, and M.E. Jakubauskas. 2006. Quantifying relationships between bird and butterfly community shifts and environmental change. Ecological Applications 16(1): 380-393.
    • 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.
    • Layberry, R.A., P.W. Hall, and J.D. LaFontaine. 1998. The Butterflies of Canada. University of Toronto Press. 280 pp. + color plates.
    • Maxell, B.A. 2016. Northern Goshawk surveys on the Beartooth, Ashland, and Sioux Districts of the Custer-Gallatin National Forest: 2012-2014. Montana Natural Heritage Program. Helena, MT. 114pp.
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Silvery Blue — Glaucopsyche lygdamus.  Montana Field Guide.  .  Retrieved on , from