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Several authorities do not include Montana in the range of this species (Scott 1986; Ferris 1993; Glassberg 2001; Guppy and Shepard 2001; Pyle 2002; Warren 2005). The confusion seems to center on whether or not to treat the christina form as a full species (see Christina Sulphur, C. christina, account) or as a subspecies of C. occidentalis (Hammond and McCorkle 2003; Scott et al. 2006). Scott et al. (2006) refer to the C. alexandra-occidentalis complex (part of the legume-feeding species) as a "stenchospecies" for taxa that "will stink up every person studying them even if he does a thorough 'ideal' study" (Scott et al 2006:1). Given the taxonomic uncertainty and instability, this account probably includes information pertaining to more than one species.
[From Ferris and Brown 1981; Scott 1986; Ferris 1993; Opler and Wright 1999; Glassberg 2001; Scott et al. 2006] Forewing 2.4-2.9 cm. Fringes pink; wing coloration variable. Uppersurface yellow (to whiteish in females) with black scaling at wing base, male with narrow black border border; female with reduced or absent black border; with small black forewing cell spot, pale to bright orange hindwing discal cell spot. Undersurface of forewing yellow; hindwing yellow to golden, with evenly scattered dusting of black scales, a dark smudge near leading margin, cell spot large, pearly, round, rimmed with dark red, often with small satellite above, no marginal markings.
One flight, late May through June (Scott 1986). May to September (Glassberg 2001). Early May to late September in Oregon and Washington (Pyle 2002; Warren 2005), June to September in British Columbia (Guppy and Shepard 2001).
Best determined by a combination of undersurface of hindwing yellow to golden, with evenly scattered dusting of black scales, a dark smudge near leading margin, cell spot large, pearly, round, rimmed with dark red, often with small satellite above, no marginal markings.
Open areas, including open pine and Douglas-fir forest, montane meadows, roadsides, powerline corridors, to treeline (Scott 1986; Ferris 1993; Opler and Wright 1999; Glassberg 2001; Guppy and Shepard 2001; Pyle 2002; Warren 2005; James and Nunnallee 2011). In Glacier National Park, Montana reported from xeric montane meadows and above treeline in alpine terrain (Debinski 1993), but this may pertain to C. christina depending on taxonomy.
Larval food plants include native and exotic Lathyrus (multiple species), Lupinus (multiple species), Melilotus, and Vicea (multiple species) (Scott 1986; Ferris 1993; Graves and Shapiro 2003; Warren 2005; James and Nunnallee 2011), possibly Lotus (Scott 1992). Adults feed on flower nectar (including Apocynum, Asclepias, Brodiaea, Calochortus, Cirsium, Lilium, Taraxacum) and mud (Pyle 2002; James and Nunnallee 2011; Scott 2014).
Limited information, given the taxonomic confusion of the species complex. Females lay eggs singly on the upper surface of host plant leaves (Scott 1986; James and Nunnallee 2011). Eggs hatch in about 6-7 days (depending on temperature), reach L3 instar in about 17-20 days post egg-hatch then hibernate (enter diapause), develop further to L5 instar and pupate in about 20 days after exiting diapause in spring (depending on temperature); adults eclose (emerge from pupae) in about 7 weeks (James and Nunnallee 2011). Larvae eat host plant leaves, build no nests, overwinter as L3 instar in folded leaf (Pyle 2002; James and Nunnallee 2011). Males patrol throughout the day in valley bottoms, hillsides, open woods, meadow edges, streamsides, in search of females (Scott 1975b, 1986; James and Nunnallee 2011).
Literature Cited AboveLegend:    View Online Publication
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.
Ferris, C.D. 1993. Reassessment of the Colias Alexandra Group, the Legume-Feeding Species, and Preliminary Cladistic Analysis of the North American Colias (Pieridae: Coliadinae). Bulletin of the Allyn Museum 138: 1-91.28.
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.
Graves, S.D. and A.M. Shapiro. 2003.Exotics as host plants of the California butterfly fauna. Biological Conservation 110: 413-433.
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.
Hammond, P.C. and D.V. McCorkle. 2003. A new desert subspecies of Colias occidentalis (Pieridae) from southeastern Oregon. Journal of the Lepidopterists' Society 57(4): 274-278.
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. 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. 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., M.S. Fisher, N.G. Kondla, S. Kohler, C.S. Guppy, S.M. Spomer, and B.C. Schmidt. 2006. Taxonomic studies and new taxa of North American butterflies. Papilio new series #12. 80 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.
Layberry, R.A., P.W. Hall, and J.D. LaFontaine. 1998. The Butterflies of Canada. University of Toronto Press. 280 pp. + color plates.
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Western Sulphur — Colias occidentalis.  Montana Field Guide.  Montana Natural Heritage Program.  Retrieved on September 27, 2022, from https://FieldGuide.mt.gov/speciesDetail.aspx?elcode=IILEPA8270