Skippers: Laguna Mountains skipper
(Pyrgus ruralis lagunae)
(Lepidoptera: Hesperiidae: Pyrginae)
Profile prepared by Scott Hoffman Black and Mace Vaughan
The Laguna Mountains skipper is only known from a handful of sites in San Diego County, California, in the Laguna Mountains and on Mount Palomar. It occupies montane meadow habitats between 4,000 and 6,000 feet altitude within yellow pine forests. The larvae of the Laguna Mountains skipper feed solely on Cleveland’s horkelia, a plant that is similarly restricted to montane meadows in San Diego County and the neighboring Riverside County. A major factor in the decline of the Laguna Mountains skipper is the decreasing abundance of their hostplant due to grazing and trampling by cattle.
On April 2, 2009, The Xerces Society submitted a letter signed by over 30 scientists to the U.S. Fish and Wildlife Service asking for continued conservation of this species. Read the letter.
Xerces Red List Status: Critically Imperiled Other Rankings: Canada – Species at Risk Act: N/A Canada – provincial status: N/A Mexico: N/A USA – Endangered Species Act: Endangered USA – state status: None NatureServe: G5T1 IUCN Red List: N/A
There have been limited surveys for the animal but for four of the last six years (1994 – 2000), surveys in the Laguna Mountains have never recorded more than two adults in any single year. Estimates for the Palomar Mountains are that the skipper seems to be holding its own but at low numbers of individuals. There is a fairly strong population at Mendenhall Meadow. The annual populations are so small—no more than a few hundred individuals may exist each year—that this taxon could easily slip to extinction.
It was designated a Federal Endangered Species in January 1997 (Federal Register: 62- 2313).
Recovery plan (ESA): None.
Critical habitat (ESA): None designated.
The California Endangered Species Act does not allow listing of insects, so despite its precarious status, the Laguna Mountains skipper has no protection under state legislation. The California Department of Fish and Game includes this butterfly on its Special Animals list.
The Laguna Mountains skipper is a small (~3 cm wingspan), checkered member of the family Hesperiidae (Skippers). It is similar to the other nominate Pyrgus ruralis subspecies, P. r. ruralis, but can be distinguished by the extensive white wing markings rather than the overall black coloration of spp. ruralis.
Pyrgus ruralis lagunae Scott, 1981. The Laguna Mountains Skipper is one of two subspecies of Pyrgus ruralis, and is only known from higher elevation areas of southern California. The other, P. r. ruralis, is much more widespread, occurring over much of the western U.S.
The larvae of the Laguna Mountains skipper feed solely on Cleveland’s horkelia (Horkelia clevelandii), a perennial in the rose family. There appear to be two adult flight seasons each year during which the butterflies mate, one in mid spring (April-May) and a second in late summer (June-July). Adults lay eggs on the underside of horkelia leaves, apparently preferring plants on thin rocky soils. Cleveland’s horkelia is important to the adults as well, because they rely heavily on the larval host plant as a nectar source.
The Laguna Mountains skipper is only known from San Diego County, California. It occupies montane meadow habitats between 4,000 and 6,000 feet altitude within yellow pine forests of the Laguna Mountains (where a single population survives) and Mount Palomar (six sites).
A main factor in the decline of the Laguna Mountains skipper may be the decreasing abundance of their host plant, Cleveland’s horkelia (Horkelia clevelandii). This plant is restricted to montane meadows in San Diego and Riverside Counties. These grasslands have been degraded through development, grazing, and recreational activities. Grazing and trampling by cattle seem to be the principal threats, especially during the second (late summer) brood period when there is less alternative fodder available to the cattle due to the dry conditions.
The montane meadows that support populations of the larval hostplant, Cleveland’s horkelia, must be protected. Grazing pressure is a major factor limiting the growth and availability of the hostplant on those meadows that remain. There is likely only a single population of the Laguna Mountains skipper remaining in the Laguna Mountains. It would be a great shame for the butterfly to be extirpated from its namesake range.
There is a need for more surveys for additional individuals and populations and for additional studies of the natural history of the butterfly and of the impacts of grazing and other threats.
Brown, J. W. 1991. Sensitive and Declining Butterfly Species (Insecta: Lepidoptera) in San Diego County, California. unpub. manuscript, Dudek and Associates, Inc.
Encinitas CA. Hickman, J. C. (ed.). 1993. The Jepson Manual of Higher Plants of California. University of California Press, Berkeley. p. 955.
Levy, J. N. 1994. Status of the Laguna Mountains skipper (Pyrgus ruralis lagunae J. Scott). Biological survey and analysis prepared for the Forest Service, U.S. Department of Agriculture.
—. 1996. Status of the Laguna Mountains skipper butterfly: Interim Report 1995-1996. Forest Service, U.S. Department of Agriculture.
—. 1997. Status of the Laguna Mountains skipper butterfly. Report of field activities: 1995-1997. Forest Service, U.S. Department of Agriculture.
Mattoni, R. and T. Longcore. 1998. Field studies and conservation planning for the endangered Laguna Mountain skipper, Pyrgus ruralis lagunae.
Murphy, D. D. 1990. A report on the California butterflies listed as candidates for endangered status by the United States Fish and Wildlife Service. Draft Report for the California Department of Fish and Game, Contract No. c-1755. 60 pp.
Pratt, G. G. 1999. Laguna Mts Skipper in the Cleveland National Forest. 1999 Survey. Prepared for the Cleveland National Forest.
Scott, J. A. 1981. New Papilionoideae and Hesperiidae from North America. Papilio (new series) 1:1-12.
U.S. Fish and Wildlife Service. 1995. Biological/Conference Opinion on the Cleveland National Forest Grazing allotments, San Diego County, California (1-6-95-F-20)
U.S. Forest Service. 1995. Biological Assessment for Grazing Activities on the Cleveland National Forest, San Diego County, California.
U.S. Fish & Wildlife Service; Threatened and Endangered Species System: Laguna Mountains Skipper (Accessed 9/17/08)
U.S. Forest Service; Biological Opinion issued by the U.S. Fish & Wildlife Service on Laguna Mountains Skipper in the Cleveland National Forest. (Accessed 3/30/05)
University of California at Berkeley; Essig Museum of Entomology: California’s Endangered Insects, Laguna Mountains Skipper (Accessed 3/30/05)
American Zoo and Aquarium Association, Butterfly Conservation Initiative; Profile: Laguna Mountains Skipper (Accessed 9/17/08)
Nature Serve Explorer (Accessed 3/30/05)
Black, S. H., and D. M. Vaughan. 2005. Species Profile: Pyrgus ruralis lagunae. In Shepherd, M. D., D. M. Vaughan, and S. H. Black (Eds). Red List of Pollinator Insects of North America. CD-ROM Version 1 (May 2005). Portland, OR: The Xerces Society for Invertebrate Conservation.