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Pale Swallowtail - Pterourus eurymedon
Native Species
Global Rank:
G5
State Rank:
S5
Agency Status
USFWS:
USFS:
BLM:
External Links
General Description
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 4.4-4.8 cm. The only black-and-white swallowtail in the west, tail long and twisted. Uppersurface creamy white (possibly creamy but not yellow) with black stripes and a thick black wing-border, black bar in forewing cell wide, shiny blue hindwing spots reduced (except for some females), orange caudal spots can be extensive.
Phenology
One flight, mostly June (May to June in central California), several flights late March to August in southern California (Scott 1986). Mostly May to July, but April to September along the Pacific Coast (Glassberg 2001). One flight, late May to July in the Rocky Mountain states (Ferris and Brown 1981). Mid-May to mid-July in Colorado (Scott and Epstein 1987), mid-April to early October in Oregon and Washington (Pyle 2002), mid-April through September in Oregon (Warren 2005), late May to mid-July in southern British Columbia (Threatful 1988; Guppy and Shepard 2001).
Diagnostic Characteristics
Best determined by a combination of pointed wings, white and black stripes, and broad black wing borders.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Southern British Columbia and southwestern Alberta east to Montana and the Black Hills of South Dakota, south to New Mexico, southern Utah, northern Nevada, southern California and northern Baja California (Opler and Wright 1999; ); 1830 m to 2745 m elevation in the Rocky Mountain states (Ferris and Brown 1981), 1829 m to 3200 m in Colorado (Brown 1957; Scott and Scott 1978), to about 2745 m elevation in northern California (Shapiro 1977), near sea level to at least 2499 m in Oregon (Warren 2005), to 640 m elevation in southeastern British Columbia (Threatful 1988). In Montana, reported throughout the western 1/3 of the state and diagonally southeast to Rosebud and Custer counties, with no reports from the northeastern 1/4 of the state (Kohler 1980; Stanford and Opler 1993; FLMNH Lepidopterists' Society database); to at least 1890 m elevation.
Observations in Montana Natural Heritage Program Database
Number of Observations: 118
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Migration
Non-migratory. Males may move several kilometers between hilltops while searching for females (Scott 1986).
Habitat
Deciduous woodlands, chaparral, conifer forest, moist canyons (Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001). In Glacier National Park, Montana reported from xeric and mesic montane meadows (Debinski 1993); in the Greater Yellowstone Ecosystem, reported from stream sides, open woodlands, hilltops (Debinski and Pritchard 2002).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Grassland Systems
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
Food Habits
Larval food plants are native and exotic members of the Rosaceae, including Amelanchier, Crataegus (multiple species), Holodiscus, Malus, and Prunus (several species), members of the Rhamnaceae, including Ceanothus (several species), Frangula, Rhamnus, members of the Grossulariaceae, including Ribes, and members of the Betulaceae, including Alnus and Betula (Emmel and Emmel 1963; Scott 1986, 1992, 2006; Guppy and Shepard 2001; Graves and Shapiro 2003; Warren 2005; James and Nunnallee 2011). Adults feed on flower nectar (including Apocynum, Aquilegia, Carduus, Ceanothus, Cercis, Cirsium, Delphinium, Dentaria, Dianthus, Eriodictyon, Erysimum, Hesperis, Jamesia, Lilium, Lupinus, Oxytropis, Penstemon, Phlox, Physocarpus, Prunus, Rubus, Solidago), sprinkler water drops, and mud (Pyle 2002; Warren 2005; Scott 2014).
Reproductive Characteristics
Females lay eggs singly on host plant leaf, usually on uppersurface near base (Scott 1986, 1992, 2006; James and Nunnallee 2011). Eggs hatch in about 4-10 days (depending on temperature), develop to L5 instar and pupae in about 40-42 days post egg-laying, depending on temperature (Guppy and Shepard 2001; James and Nunnallee 2011). Larvae feed on host plant leaves (usually from leaf edges), do not make nests but spin light silk pad on concave upper leaf surface on which to rest, overwinter as pupae on host plant stem (Scott 1979; James and Nunnallee 2011). Males patrol and sometimes perch throughout the day on hilltops, forest edges, stream banks in search of females (Scott 1975; Guppy and Shepard 2001; Pyle 2002).
Stewardship Responsibility
References
- Literature Cited AboveLegend:
View Online Publication
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. and J.A. Pritchard. 2002. A field guide to the butterflies of the Greater Yellowstone Ecosystem. Lanham, MD: Roberts Rinehart Publishers. 107 p.
- Emmel, J.F. and T.C. Emmel. 1963. Larval food-plant records for six western papilios. Journal of Research on the Lepidoptera 1: 191-193.
- 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.
- 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.
- 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.
- Scott, J.A. and M.E. Epstein. 1987. Factors affecting phenology in a temperate insect community. American Midland Naturalist 117(1): 103-118.
- Shapiro, A.M. 1977. The alpine butterflies of Castle Peak, Nevada County, California. Great Basin Naturalist 37(4): 443-452.
- 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.
- 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
- 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.
- Opler, P.A., K. Lotts, and T. Naberhaus, coordinators. 2010. Butterflies and moths of North America. Big Sky Institute, Bozeman, MT. Available at: www.butterfliesandmoths.org (Accessed 15 June 2015).
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