Rocky Mountain Dotted Blue - Euphilotes ancilla
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.1-1.3 cm. Fringes white and weakly checkered. Uppersurface of male deep blue with medium black border, hindwing aurora usually absent but sometimes present. Female brown, with orange aurora varying wide to absent, terminal line thin. Undersurface light blue-gray, forewing often suffused with smoky dark-gray, hindwing with prominent black spots smaller than on forewing, submarginal orange aurora usually composed of unconnected spots, capped with inward-pointing black.
One flight; mostly June to July (Scott 1986). Late May to July (Glassberg 2001). Late May to early July in Oregon (Warren 2005). Early season cohort early May to early July, late season cohort mid-July to mid-August in southern Nevada (Austin et al. 2008).
Difficult to distinguish in field from closely-related species based on gross external characters, necessitating data on date, locality, larval hostplant, ultimately morphology of adult genitalia (Glassberg 2001; Guppy and Shepard 2001; Austin et al. 2008). Helpful characteristics include presence of the submarginal orange aurora on both surfaces of the hindwing with orange in disconnected spots on the undersurface, the wing fringes white and weakly checkered, undersurface of forewing often suffused with smoky dark-gray, hindwing with prominent black spots smaller than on forewing.
Southern Alberta and southern Saskatchewan south through southern Idaho, Wyoming, Colorado and northeastern Utah in the Rocky Mountain region to extreme northern New Mexico, and along the eastern base of the Cascades and Sierra Nevada from northern Washington to southern California and southern Nevada; not yet reported in British Columbia (Opler and Wright 1999; Glassberg 2001; Guppy and Shepard 2001; Pyle 2002; Warren 2005); 1676 m to 2590 m elevation in Colorado (Brown 1957; Ferris and Brown 1981), 1341 m elevation in southeastern Oregon (Warren 2005). In Montana, reported from at least 15 counties in the western half of the state (Kohler 1980; Stanford and Opler 1993) to at least 1554 m elevation, since then reported from extreme southeastern Montana (FLMNH Lepidiopterists' Society database). Locally rare in the north, common to abundant in the south (Glassberg 2001).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Rocky slopes and hilltops, exposed flats, desert washes, canyons, sagebrush steppe, open woodland (Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002). In Glacier National Park, Montana reported from transition habitat between low elevation and alpine (Debinski 1993), in the Greater Yellowstone Ecosystem reported from xeric montane meadows dominated by sagebrush (Debinski et al. 2013).
Larval food plants include several species of Eriogonum, especially E. umbellatum in the Rocky Mountain region (Ferris and Brown 1981; Scott 1986, 1992, 2006). Adults feed on flower nectar (including Chrysothamnus, Eriogonum, Heterotheca, Medicago) and mud (Scott 2014).
Females lay eggs singly on host plant flowers or flower buds (Scott 1986, 1992, 2006). Larval development poorly described (but see Austin et al. 2008), is likely similar to E. enoptes of which it was once considered a subspecies (see Ferris and Brown 1981; Scott 1986). Eggs of E. enoptes hatch about 5 days post-oviposition, develop from L1 instar to L4 instar and pupation in about 23 days, pupae overwinter (diapause), usually in soil or debris at base of host plant. Larvae build no nest, eat host plant flowers and fruits, are tended by at least five species of ants (Scott 1979, 1986; Austin et al. 2008; James and Nunnallee 2011). Males patrol throughout the day over all kinds of topography near host plants while seeking females (Scott 1975b, 1986).
- Literature Cited AboveLegend: View Online Publication
- Austin, G.T., B.M. Boyd, and D.D. Murphy. 2008. Euphilotes ancilla (Lycaenidae) in the Spring Mountains, Nevada: more than one species? Journal of the Lepidopterists' Society 62(3): 148-160.
- 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.
- 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. 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.
- 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
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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.
- 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.
- 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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