Blues: insular blue (Plebejus saepiolus littoralis)
Profile prepared by The Xerces Society for Invertebrate Conservation
This coastal species is known from three sites in Oregon and California.
Heritage Global Rank: G51T3
Heritage State Rank: California (SNR-Unranked); Oregon (S1-Critically Imperiled); Washington (SNR-Unranked)
At ssp. level littoralis/insulanus level it is undescribed.
Description of species Plebejus saepiolus: Green or pale green with white lateral line edged with red or pink (Allen et al. 2005). Pyle also states that caterpillars, have green and reddish forms (Pyle 2002).
Description of species Plebejus saepiolus: Size 1 – 1¼” (26-32mm). Sexes dimorphic.
Male upperside of wing: A grainy blue with green overtones, a black border, and a distinct black bar in the FW cell.
Female upperside of wing: blue brown to copper, often with orange and sometimes with blue at the base.
Male underside of wing: light gray with turquoise scaling at the base.
Female underside is tan to brownish gray, sometimes with blue at the base.
Male and female undersides have various black spotting but almost always have one or more pairs of pronounced, opposing spots near the anal angle of the hind wing, marginal dashes faced by submarginal chevrons, capping a subtle orange or rusty patch between them (female lacks orange zig-zags of copper) (Pyle 2002; Opler 1999).
P.s. littoralis is differentiated from other greenish blue subspecies by having fewer black spots with unique white halos and is slightly larger then other Greenish Blue subspecies (Pyle 2002). The species is considered a distinct and valid subspecies Emmel et al. 1998; Pyle pers. com. 2005).
Plebejus saepiolus littoralis (Emmel, Emmel, Mattoon 1998)
Common Name: “The coastal greenish blue” – insular blue (subspecies of greenish blue) Note: This species is being referred to as the coastal greenish blue because the common name insular blue can be confused with another subspecies of greenish blue (Plebejus saepiolus insulanus).
Most life history details of this coastal subspecies appear to be unknown or have not been published. According to (Emmel et al. 1998) the subspecies flies in a single brood from early May to mid June. Specimens have been collected from 26 May (Rock Creek) to 3 July (Coos County Line, worn specimen), with most collection dates for the month of June. (Evergreen Aurelian records).
There is additional information for the species. Caterpillars are found on leaves of clovers from April – June (Allen et al. 2005) Adults are on the wing from late April to mid August, peaking in June – July. (Pyle 2002; Opler 1999). Eggs are laid in clover flowers (Trifolium monanthum, T. longipes, T. wormskiodldii, and probably others) (Pyle 1981). The species overwinters as early instar caterpillar in flower head of host clover (Allen et al. 2005).
Typically along stream edges, bogs, or wet meadows but also along drier sites that have blooming clovers such as roadsides and open meadows. The name littoralis means “of the shore”?’.”; also “?’found on the immediate coast?’”; and “?’sand dunes?’” are all they say in the description of the ssp. littoralis. The colony at the Coquille River Lighthouse favored the moist depressions in the lee of sand dunes along the access road.
Little is known about the historic distribution. Historical data shows the coastal subspecies present from Lake Earl, Del Norte Co., CA; in Oregon, from Curry County- 2 mi N Gold Beach; Cape Blanco; on Coos County line; Coos County- Coquille River Lighthouse; Lane County- Rock Creek; Lincoln County- De (Devils) Lake. A single record from Clatsop County (near Elsie) may have been due to a mislabeled specimen (Warren 2005).
Greenish blue’s range extends throughout the western and northern United States and transborder Canada (Pyle 2002). P.s. littoralis is found in Curry and Coos counties and a mid-coastal colony in Lane County in Oregon (Pyle 2002) as well as in Del Norte County in California (Emmel et al. 1998).
The Oregon Natural Heritage Program lists locations as Curry and Lane Counties. Specifically it has been found at Rock Creek/Big Creek site on Siuslaw National Forest. The Lighthouse, N side of Coquille River mouth also appears to be on Siuslaw National Forest land and at Cape Blanco on US Coast Guard and Oregon State Parks land. It is also found on the immediate coast of Del Norte County (Emmel et al. 1998)
Undocumented at this time, but may include the conversion of coastal habitat to homes, succession of moist meadow or dune habitat to shrub/woodland habitat, competition from weeds, trampling by humans, livestock or offroad vehicles, or other natural ecological factors. Some of these same threats have been documented for the seaside hoary elfin (Ross 2005) and the Oregon silverspot, butterflies that are also confined to coastal habitats.
Surveys (ssp. littoralis/insulanus) can be used to more accurately determine the current distribution of the coastal greenish blue and to establish its local relative abundance and the threats to populations wherever they occur. Historical sites could be visited first to determine the presence/absence of the butterfly there. Searches for additional populations could also be conducted, given the paucity of historical records for the taxon.
Scale is important when managing habitat for at risk butterflies. Division of a site into several management units is important, with butterfly habitat within a site evenly divided among these management units. Individual units could be managed in a rotation that assures at least 2/3 of the habitat is left unmanaged at any one time (Dana 1991), with three growing seasons between management activities in any one unit. This rotation should allow sufficient time for numbers to rebuild before the next management action (Dana 1991).
More study is needed to determine management actions at known sites. Managers may need to consult with an expert in managing habitat for butterflies before moving forward on restoration projects or projects that may adversely impact the sites.
Allen, Thomas J.; Brock, Jim P.; and Glassberg, Jeffrey. 2005. Caterpillars In the Field and Garden, A Field Guide to the Butterly Caterpillars of North America. Oxford University Press, Oxford, New York.
Dana, R.P. 1991. Conservation management of the prairie skippers Hesperia dacotae and Hesperia ottoe: Basic biology and threat of mortality during prescribed spring burns. University of Minnesota. Minnesota Agr. Exp. Sta. Bull. 594-1991(AD-SB-5511-S). 62 pp.
Emmel, J.F, T.C. Emmel and S.O. Mattoon. 1998. New Polyommatinae Subspecies of Lycaenidae (Lepidoptera) from California. Pages 171-200 in T. C. Emmel, editor. Systematics of western North American butterflies. Mariposa Press, Gainesville, Florida. 878pp.
Opler, Paul. 1999. A Field Guide to Western Butterflies. 2d ed. Houghton Mifflin Company, Boston, Massachusetts.
Pyle, Robert Michael. 2002. The Butterflies of Cascadia, A Field Guide to All the Species of Washington, Oregon, and Surrounding Territories. Seattle Audubon Society, Seattle, Washington.
Warren, Andrew D. 2005. Lepidoptera of North America 6, Butterflies of Oregon: Their Taxonomy, Distribution, and Biology. Department of Zoology, Oregon State University, Corvallis, Oregon.