Sulphurs: Intermountain sulphur (Colias occidentalis pseudochristina = Colias christina psuedochristina)
(Arthropoda: Insecta: Lepidoptera: Pieridae) Profile prepared by Sarah Foltz Jordan, The Xerces Society for Invertebrate Conservation
The intermountain sulphur occurs in eastern Washington and Oregon, along the Snake River in Idaho, and in western Utah. The habitat for this subspecies is steep, sunny slopes with sage brush and scattered ponderosa pine. Pesticide use poses serious threats to this butterfly, and aerial spraying of Btk (Bacillus thuringiensis var. kurstaki) for forest defoliating moths has weakened and eliminated several populations of this subspecies in eastern Oregon (Hammond 2009, pers. comm.). Although this taxonomically unstable subspecies has been classified differently by various authors (e.g. Pyle 2002, Warren 2005), the most recent treatment by Pelham (2008) places it in the Colias christina species, with which it shares the trait of having dorsal ultraviolet reflective scales in some males.
Adult: Bright yellow or yellow-orange sulphur butterfly with black dorsal front wing margins in males. This subspecies is identified as follows (Pyle 2002, Warren 2005, Opler et al. 2006):
• Medium-sized; 4.5 – 6.3 cm (1.75 to 2.5 in.) wingspan • Dorsal surface of the male yellow, with orange over-scaling in 96% of males • Dorsal surface of some males with ultraviolet reflective scales • Dorsal surface of female yellow to light cream or (rarely) white • Front wing tips pointed • Black margin on dorsal front wing narrow and solid in males, and smudgy, broken or absent in females • Ventral hind wing with a large, pearly spot with a reddish rim
Since there are no other subspecies of Colias christina (= occidentalis) in the region, the most confounding species is the orange sulfur (Colias eurytheme), which differs in having the ventral hind wing discal spot double-ringed (as opposed to simple-ringed) (Hammond 2009, pers. comm.). Additionally, while both C. christina pseudochristina and C. eurytheme can have orange over-scaling, the orange color is more limited and suffused in C. c. pseudochristina, without a central orange patch on each wing (Pyle 2002).
Immature: The eggs, larvae, and pupae are difficult to find and to identify. The immature stages of closely related C. occidentallis sullivani (= C. christina sullivani) are described and figured in Harry (2005).
Depending on seasonal conditions, adults of this subspecies fly mostly in late May (e.g. Asotin Co. Washington, 3400 ft.), but individuals have been collected at higher elevations through late June (Minam River, 3000 ft.) and early July (upper Imnaha River, 4400 ft.). The flight periods of both C. occidentalis and C. christina are from May-September, peaking in June through July. Oblong eggs are laid singly on the leaves of the host plant (see Neill 2001), and overwinter in the larval stage. The larvae of this subspecies feed on Lathyrus species, including L. brachycalix, L. lanzwertii, L. nevadensis, and L. pauciflorus (Hammond 2009, pers. comm.). The Asotin County population in Washington was reported to feed on L. pauciflorus (reviewed in Warren 2005). Adults of C. christina use a variety of plants as nectar sources, and males may occasionally be seen frequenting mud puddles (Opler et al. 2006). Nothing is known about colonization ability, but the species appears to be a strong flier.
Range-wide: The subspecies is found from the eastern Blue Mountains in Washington, through the Blue and Ochoco Mountains in Oregon, along the Snake River in Idaho, and south into western Utah. One population is known in Washington, probably fewer than five populations in Oregon, and unknown numbers in Idaho and Utah.
Washington: This subspecies is known from two townships in southern Asotin County, on the Oregon border. The percentage of the range that is occupied is unknown, and no population estimates are available.
Oregon: Numerous locations in northeast Oregon, in the Ochoco, Aldrich, Blue, and Wallowa mountains.
Federal Land: In Washington, this species is suspected on Umatilla National Forest and BLM land in Vale District-Washington. In Oregon, it is documented from Wallowa-Whitman National Forest and suspected on the Umatilla National Forest and BLM land in the Vale District-Oregon.
This species inhabits open woodland from 1036 to 1524 m (3400 to 5000 ft.), including meadows, roadsides, and open forest. Warren (2005) states that members of this subspecies are most often found on steep sunny slopes at the ecotone between forest and shrubsteppe or grassland habitats. Hammond (2009, pers. comm.) describes the subspecies habitat as sage brush with scattered ponderosa pine, including both south- and east-facing slopes. The larvae of this subspecies feed on Lathyrus species, including L. brachycalix, L. lanzwertii, L. pauciflorus, and. L. nevadensis (Hammond 2009, pers. comm.). The Asotin County population in Washington was reported to feed on L. pauciflorus (reviewed in Warren 2005). Adults of C. christina use a variety of plants as nectar sources, and males may occasionally be seen frequenting mud puddles (Warren 2005).
Inventory: Since there are relatively few records of this subspecies in Oregon and Washington, and many of the existing populations have been negatively influenced by Btk spraying (Hammond 2009, pers. comm.), further surveys at known and potential sites will be valuable in evaluating the taxonomic status, range, population characteristics, and conservation needs of this subspecies.
Management: Protect all known and potential sites from practices that would adversely affect any aspect of this butterfly’s life-cycle. Avoid insecticide/herbicide use in or near known sites and manage grazing to reduce impacts to Lathyrus, the larval food plant.
Research: Although there are reasonable arguments for the current taxonomic placement of this subspecies within C. christina, DNA-sequence analysis of this subspecies and other members of C. christina and C. occidentalis could elucidate the taxonomic placement of these groups (Warren 2005).
Dornfeld, E.J. 1980. The Butterflies of Oregon. Timber Press, Forest Grove, Oregon. 276 pp.
Hammond, Paul. 2009. Personal communication with Sarah Foltz, Xerces Society for Invertebrate Conservation.
Harry, J. 2005. Immature stages of Colias occidentalis sullivani from Oregon (Lepidoptera: Pieridae). The Taxonomic Report 6(2): 1-4.
NatureServe. 2009. “Colias occidentalis pseudochristina.” NatureServe Explorer: An online encyclopedia of life [web application]. Feb. 2008. Version 7.0. NatureServe, Arlington, Virginia. 15 Feb. 2009. .
Neill, W. 2001. The guide to butterflies of Oregon and Washington. Westcliffe Publishers, Englewood, Colorado. 160 pp.
Opler, P.A., Pavulaan, H., Stanford, R.E. and M. Pogue, coordinators. 2006. Butterflies and Moths of North America. Bozeman, MT: Big Sky Institute. 9 Feb. 2009. .
Oregon Department of Agriculture (ODA). 2008. Oregon Grasshopper and Mormon Cricket Survey Map. Oregon Department of Agriculture (ODA) in Cooperation with USDA-APHIS-PPQ. Salem, Oregon.
Pelham, J. 2008. A catalogue of the butterflies of the United States and Canada with a complete bibliography of the descriptive and systematic literature. Journal of Research on the Lepidoptera 40: 658 pp.
Pyle, R.M. 2002. Butterflies of Cascadia. Seattle Audubon Society, Seattle, Washington. 420 pp.
Walenta, D.L. 2008. Summary Report. Economic Impact of Grasshopper Infestations to Agricultural Producers in Baker, Union, and Wallowa County of Northeastern Oregon. Oregon State University (OSU) Extension Service, Corvallis, Oregon.
Warren, A.D. 2005. Butterflies of Oregon: Their Taxonomy, Distribution, and Biology. Lepidoptera of North America 6. Contributions of the C.P. Gillette Museum of Arthropod Diversity. Colorado State University, Fort Collins, Colorado. 408 pp.