Skippers: mardon skipper (Polites mardon)

(Lepidoptera: Hesperiidae: Hesperiinae)

Profile prepared by Scott Hoffman Black and Mace Vaughan, The Xerces Society for Invertebrate Conservation

The mardon skipper is a small, tawny-orange butterfly dependent upon native grasslands in Washington, Oregon, and northwest California. Mardon skippers were likely more widespread and abundant before European settlers reached the region. These grasslands have declined dramatically in the past 150 years due to agricultural and residential development, fire suppression, livestock grazing, and introduction of exotic species. For example, in western Washington, more than 95% of the native prairie grasslands have been destroyed.

red list profile

conservation status

Xerces Red List Status: Imperiled
Other Rankings:

Canada – Species at Risk Act: N/A
Canada – provincial status: N/A
Mexico: N/A
USA – Endangered Species Act: N/A
USA – state status: WA: Endangered
NatureServe: G2G3 (01Sep1998)
IUCN Red List: N/A

The mardon skipper has recently been extirpated from four sites in south Puget Sound and one in the southern Washington Cascades and the current status of four other sites in Washington is uncertain. Most of the remaining sites are very small, most measuring just a few acres. Most sites support less than fifty butterflies.

The mardon skipper remains a federal candidate species. The State of Washington Department of Fish and Wildlife (WDFW) lists the Mardon Skipper as state endangered and are implementing conservation measures in Washington. Neither Oregon nor California allows insects to receive protection under their respective endangered species legislation.

description and taxonomic status



Photo by Donald Gudehus
Please contact The Xerces Society for information on how to obtain permission to use this image.

The mardon skipper (Polites mardon) is a small (20-24 mm; <1 inch), tawny-orange butterfly with a stout, hairy body. The upper surface of both wings is orange with broad dark borders. The wings from below are light tan-orange with a distinctive pattern of light yellow to white rectangular spots. Males are smaller than females and have a small, dark brown streak (stigma) on the upper surface of the forewing. Like most hesperiine skippers, mardon skippers have a fast, skipping flight, bent antennae clubs, and a characteristic basking posture in which the forewings are held at a 45-degree angle and the hind wings are fully spread.

Polites mardon (W. H. Edwards), 1881. The mardon skipper has two subspecies, P. m. mardon (W. H. Edwards), 1881, and P. m. klamathensis Mattoon, J. Emmel, & T. Emmel, 1998.

life history

Mardon skippers complete one life cycle annually, and adults emerge from chrysalids in late-spring or early-summer (in Washington, emergence is between May and July) for a month-long flight period. After mating, females deposit their eggs into native bunchgrass where they hatch after 6 to 7 days. Larvae feed on fescue, oatgrass, and  a variety of other grasses for about 3 months, overwinter as larvae, then pupate in the early spring.

In the Puget lowlands, the mardon skipper is found in prairie and meadow habitat with abundant Idaho fescue (Festuca idahoensis). The short, open stature of native, fescue bunchgrass stands allows mardon skippers to readily access both nectar and oviposition plants. Larvae feed on Idaho fescue (F. idahoensis) and red fescue (F. rubra). Adults nectar from the flowers of a variety plants, but blue violet (Viola adunca) is a strongly preferred nectar source and Scotch broom (Cytisus scoparius) is strongly avoided. Nectaring has also been observed on lupine (Lupinus sp.), Idaho blue-eyed grass (Sisyrinchium idahoense), penstemon (Penstemon sp.), western (or sanddune) wallflower (Erysimum capitatum), and on the introduced garden vetch (Vicia sativa). The Oregon adults avidly visit clover (Trifolium sp.).

distribution

The historic range and abundance of mardon skippers is not precisely known because systematic and quantitative studies were not conducted prior to 1980. It is clear, however, that the species has suffered significant range contraction and population decline as the grassland habitats with which it is associated have been lost or degraded. For example, Northwest grasslands were formerly much healthier, larger, and interconnected— conditions that would have supported a greater distribution and abundance of mardon skippers.

Historically, mardon skippers were collected from three counties in Washington (Thurston, Klickitat, and Yakima), two counties in Oregon (Klamath and Jackson), and one (Del Norte) in California. The mardon skipper is now known from 37 sites located in four geographic areas: (1) southern Puget Sound, (2) the Mt. Adams area (eastern side of the Cascade Range) in southern Washington, (3) the Cascade Range in southern Oregon, and (4) Del Norte (north-coastal) California.

The subspecies P. m. mardon is found in Washington state and Del Norte County, California, and the subspecies P. m. klamathensis is found in southern Oregon.

threats and conservation needs

Threats

The mardon skipper is threatened directly and indirectly by a number of factors that degrade its obligate grasslands, including development, recreation, overgrazing, pesticides, invasive plants (and control measures for them), and succession to forest. Because butterflies like the mardon skipper are sedentary and have a low degree of vagility, maintaining the quality of occupied habitat is perhaps the most important management concern. Inevitably, these threats seldom occur in isolation and usually work in concert at particular sites to negatively impact mardon skipper habitat. None of the sites where the Mardon Skipper occurs are managed for its conservation.

Conservation needs

Most of the populations are on Forest Service, BLM or Washington State DNR land. It will be important to work with these agencies to ensure that habitat management takes this butterfly’s protection into account.

WDFW has initiated surveys and research into habitat needs of the Washington populations. There is research into the impact of grazing that has just been initiated in Southern Oregon and surveys are being initiated in California.

WDFW has just initiated research into captive rearing.

It is important that surveys are undertaken to identify all populations.

references

Barry, J. W. 1993. Predicting and Measuring Drift of Bacillus thuringiensis Sprays. Environmental Toxicology and Chemistry, Vol 12, pp. 1977-1989.

Crawford, R. C., and H. Hall. 1997. Changes in the south Puget prairie landscape. Pages 11-16 in P. V. Dunn and K. Ewing (eds). Ecology and Conservation of the South Puget Sound Prairie Landscape. The Nature Conservancy, Seattle, Washington. 289 pp.

Fleckenstein, J., and A. Potter 1999. 1997, 1998 Project summary: Puget prairie butterfly surveys. Washington Department of Natural Resources, Olympia. Unpublished Report, 21 May, 1999. 14 pp.

Mattoon, S. O., J. F. Emmel, and T. C. Emmel. 1998. The distribution of Polites mardon (Lepidoptera: Hesperiidae) in North America, and description of a new subspecies from southern Oregon. Pages 767-774 in T. C. Emmel, editor. Systematics of western North American butterflies. Mariposa Press, Gainesville, Florida. 878 pp.

Potter, A., and J. Fleckenstein. 2001. Southern Cascade Surveys for the Mardon Skipper, Summary Year 2000. Washington Department of Fish and Wildlife, Olympia 11 pp.

Potter, A., J. Fleckenstein, S. Richardson, and D. Hays. 1999. Washington State Status Report for the Mardon Skipper. Washington Department of Fish and Wildlife, Olympia 39 pp.

Pyle, R. M. 2002. The Butterflies of Cascadia. Seattle Audubon Society, Seattle, WA.

Runquist, E. 1999. Butterfly Community Surveys in the Soda Mountain Region, Jackson County, Oregon. Bureau of Land Management, Medford, OR. 27 pp.

additional resources

Xerces report – Controlled Burning and Mardon Skipper: Summary of Mardon Skipper Coon Mountain Burn Site Occupancy Study 2009-2013.

Xerces Society 2009 California mardon skipper report – fire study

Xerces Society 2008 Washington mardon skipper report

Xerces Society 2007 Oregon mardon skipper report

Xerces Society 2007 Washington mardon skipper report

Xerces Society 2007 California mardon skipper report

Xerces Society 2006 Oregon & Washington mardon skipper report

Petition to list the mardon skipper under the Endangered Species Act

mardon skipper survey form

Big Sky Institute, Butterflies and Moths of North America: mardon skipper (Accessed 1/21/09)’

NatureServe Explorer (Accessed 9/23/08)

citation

Black, S. H., and D. M. Vaughan. 2005. Species Profile: Polites mardon. 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.

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