The Mardon skipper butterfly is a candidate species. An annual review of the Mardon skipper was conducted in 2007.

Historical Status and Current Trends

The historical range and abundance of Mardon skippers is not precisely known because no studies were conducted prior to 1980. Historically, Mardon skippers were collected from three counties in Washington (Thurston, Klickitat, and Yakima); two counties in Oregon - Klamath and Jackson; and Del Norte county in California. The Mardon skipper is now known from 37 sites located in four geographic areas: southern Puget Sound and the Mt. Adams area in Washington; the Siskiyou Mountains in southern Oregon; and Del Norte, California. All these sites are small; most supporting less than 50 individuals. There are three sites in the Cascade Mountains, located between Soda Mountain and Fish Lake. Mattoon et al. (1998) recently proposed that these Oregon populations be considered a separate subspecies, Polites mardon klamathensis.

Description and Life History

The Mardon skipper is a small (20 to 24 millimeters; <1 inch), tawny-orange butterfly with a stout, hairy body. The upper surface of both wings is orange with broad dark borders. From below, the wings 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 on the upper surface of the forewings. 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.

Mardon skippers complete one life cycle annually, and adults (in southern Oregon) emerge in June and July for a month-long flight period. After mating, females deposit their eggs into native bunchgrass where they hatch after six to seven days. Larvae feed on fescue grass (Festuca sp.) for about three months and pupae hibernate through the winter.

Habitat

The Mardon skipper is found on glacial outwash prairies in the Puget Sound lowlands, where it occupies open grasslands with abundant Idaho fescue interspersed with early blue violet. In the Mt. Adams area, the Mardon skipper is found in openings, Ceanothus breaks, meadows, and fescue grasslands within Ponderosa pine savanna/woodland, at elevations ranging from 1,900 feet to 5,100 feet (Pyle 2002). The southern Oregon populations occur in meadow habitats surrounded by incense cedar (Calocedrus decurrens), white fir (Abies concolor) Douglas-fir (Psuedotsuga menziesii), Oregon grape (Mahonia spp.), bedstraw (Galium spp.), and wild cherry clover (Trifolium sp.) (Matoon et al. 1998). The population in Del Norte County California is located at the edge of a fog break area with serpentine soil.

Mardon skipper larvae feed on Idaho fescue and red fescue (F. rubra). The populations in Puget Sound use Idaho fescue, while populations in the Mt. Adams area use Idaho fescue and red fescue as well as another unidentified fescue species. Adults require a variety of nectar source plants. The short, open stature of native, fescue bunchgrass stands allows Mardon skippers to readily access nectar and oviposition plants on Puget Sound prairies. Adults prefer blue violet (Viola adunca) but will feed from a variety of flowers, though they strongly avoid Scotch broom (Cytisus scoparius). Nectaring has been observed on common vetch (Vicia sativa), prairie lupine (Lupinus sp.), Idaho blue-eyed-grass (Sisyrinchium Idahoense), penstemon (Penstemon spp.), sego lily (Calochortus subalpinus), and wallflower (Erysimum linifolium) (Pyle 2002). The Oregon adults avidly visit clover (Matoon et al. 1998).

Reasons for Decline

The major factor affecting this species is the loss of a large percentage of the original prairie grasslands upon which it depends. These grassland and savanna landscapes are threatened today by forest encroachment, native and non-native plant invasions, development, recreational activities, grazing, agricultural practices, and application of herbicides. In addition to loss of habitat, the butterflies are threatened by insecticides, control practices for invasive plants, military training, fire, and recreational activities.

References

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. 878pp.

Pyle, R.M. 2002. The Butterflies of Cascadia. Seattle Audubon Society. Seattle, WA. 420 pp.