Poweshiek Skipperling

The upper wing surface is dark brown with a band of orange along the leading edge of the forewing. The lower surface is also dark brown, but the veins of all, but the anal third of the hindwing are outlined in hoary white. This coloration gives an overall white appearance to the undersurface. Poweshiek skipperling eggs are pale yellowish green, mushroom shaped with a flattened bottom, a slightly depressed micropyle, and smooth surfaced. The head and body of the larvae is pale grass-green, with a distinctive darker green middorsal stripe and seven cream-colored stripes on each side, as documented by W.S. McAlpine.

Poweshiek skipperlings are small and slender-bodied butterflies.

Measurements
Wingspan: Approximately 0.9 to 1.2 in (2.3 to 3.0 cm)

Poweshiek skipperlings are univoltine, meaning that they have one brood or single flight period a year, with adults emerging from mid-June to early July. The actual flight period varies somewhat across the species’ range and can also vary significantly from year to year, depending on weather patterns, as documented by R.A. Royer and G.M. Marrone in 1992 and later confirmed by A.B. Swengel and S.R. Swengel in 1999. The flight period in a given locality lasts two to four weeks, and mating occurs throughout this period, as documented by T.L. McCabe and R.L. Post in 1977 and later confirmed by A.B. Swengel and S.R. Swengel in 1999.

Poweshiek skipperlings lay their eggs near the tips of leaf blades and overwinter as larvae on the host plants, as documented by the Bureau of Endangered Resources in A.B. Swengel and S.R. Swengel in 1999. In 1972, W.S. McAlpine observed hatching of larval Poweshiek skipperling after about 9 days. The number of instars can be influenced by many factors, for example larvae reared at the Minnesota Zoo, typically have six instars, as documented by C. Nordmeyer in 2021. Captive Poweshiek skipperling eggs hatched eight to nine days after oviposition, as documented by Runquist in 2013. After hatching, Poweshiek skipperling larvae crawl out near the tip of grasses and may remain stationary, with their head usually pointing downward, as documented by W.S. McAlpine in 1972. W.S. McAlpine  also observed that Poweshiek skipperling do not form shelters underground and S. Borkin later confirmed in 1995. Instead, the larvae overwinter up on the blades of grasses and on the stem near the base of the plant, as documented by S. Borkin in 2008 and later confirmed by Dana in 2008.

Poweshiek skipperlings have an annual life cycle. The short adult life span lasts two to four weeks in the summer.

The flight period in a given locality lasts two to four weeks, and mating occurs throughout this period, as documented by T.L. McCabe and R.L. Post in 1977 and confirmed by A.B. Swengel and S.R. Swengel in 1999.

Poweshiek skipperling have distinctive white veins below and limited distribution, which can help distinguish it from most other small skippers. Species that can be confused with Poweshiek skipperling vary by geographic location, habitat and time of flight. For example, a closely related species, Garita skipper, naturally occurs in Minnesota, but not in Michigan. Generally, the Poweshiek skipperling flight is later than that of the Garita skipper. Least skippers also use similar habitat as Poweshiek skipperling and can be confused by untrained individuals, but are different in appearance. The introduced European skipper looks quite different to the trained eye, but is often mistaken for Poweshiek skipperlings by those who are novices species in identification. The European skipper wings are bright golden orange above, with narrow dark margins and the hind wing veins on the underside are not noticeably lighter than the base color.

Poweshiek skipperling habitat include prairie fens, grassy lake and stream margins, moist meadows, sedge meadow and wet-to dry native prairie. Historically, the species was found on both dry and wet native prairies across the midwest. The species relies on remaining remnant, or unplowed, native prairies and has not been found in reconstructed prairies. For more detailed descriptions of historically occupied prairie habitats, refer to the 2014 listing rule and the 2015 critical habitat designation.

The disjunct populations of Poweshiek skipperlings in Michigan have more narrowly defined habitat preferences than most of its historical range, which are variously described as prairie fens in the Michigan Natural Features Inventory of 2011 and 2012. Poweshiek skipperling have been described as occupying peat domes within larger prairie fen complexes in areas that are either dominated by mat muhly or prairie dropseed, as documented by Cuthrell and others in 2013. Historical Poweshiek skipperling populations in Wisconsin were also disjunct from the population to the west and are associated with areas that contain intermixed wet prairie, wet-mesic and dry-mesic prairie habitats, as documented by S.S. Borkin in 1995 and later confirmed by Swengel in 2013.

Canadian populations of Poweshiek skipperlings are described as wet to mesic tallgrass prairie, characterized by low relief, or 3 to 7 feet, with alternating lower, wetter areas and higher, drier prairie. As documented by the Committee on the Status of Endangered Wildlife in 2003, Poweshiek skipperlings tend to be concentrated on or near the edge of the higher, drier prairie. Spikerush is frequent in the wetter areas and prairie dropseed, black-eyed Susan and palespike lobelia are frequent in the drier areas. The wet-mesic tallgrass prairies in Manitoba vary in size and occur along groves of Bur oak and trembling aspen (Populus tremuloides Michx.), as documented by P.M. Catling and J.D. Lafontaine in 1986 and later confirmed by J. Dupont in 2013. Little bluestem, big bluestem, and Indian grass were the three most commonly found grasses in managed study plots in Manitoba (Dupont 2013, p. 85). Plant species generally associated with upland, drier portions of the mesic tallgrass prairies in Manitoba include, big bluestem, pale-spike lobelia, prairie dropseed, mountain death camas, stiff goldenrod, black-eyed Susan and meadow blazing-star, as documented by Environment Canada in 2012. In lower-wetter prairies with Poweshiek skipperling, the following species are listed as often seen in Poweshiek skipperling sites: Willow (Salix spp.), sedges (Carex spp.), rushes (Juncus spp.), groundsels (Pakera spp.), tufted hairgrass, creeping bentgrass (Agrostis stolonifera), mat muhly, elliptic spike-rush, four-flowered yellow loosestrife (Lysimachia quadriflora) and common self-heal, as documented by Environment Canada in 2012. The soils where Poweshiek skipperling occurs in Manitoba are described as shallow, rocky and highly calcareous, as documented by Westwood and Borkowsky in 2004 and noted by J. Dupont in 2013.

Nectar Sources

During their flight period, adult Poweshiek skipperling depend on the availability of nectar from flowering forbs. Nectar plants vary across its geographic range. Smooth ox-eye (Heliopsis helianthoides) and purple coneflower were noted as the frequently visited nectar plants in Iowa, Minnesota and North Dakota, as documented by A.B. Swengel and S.R. Swengel in 1999. Other nectar species used were stiff tickseed (Coreopsis palmata), black-eyed Susan (Rudbeckia hirta) and palespike lobelia (Lobelia spicata), also documented by A.B. Swengel and S.R. Swengel in 1999. On drier prairie habitats in Iowa and Minnesota, purple coneflower is used almost exclusively, as documented by G. Selby in 2005. On the wetter prairie habitats of Canada and the fen habitats of Michigan, favored nectar plants are black-eyed Susan, palespike lobelia, sticky tofieldia (Triantha glutinosa) and shrubby cinquefoil (Dasiphora fruticosa ssp. floribunda), as documented by M.C. Nielsen in 1970 and later by R.W. Holzman in 1972 and others in following decades. Studies in Manitoba indicate that the most frequently utilized nectar plants are black-eyed Susan, upland white aster (Solidago ptarmicoides), and self-heal (Prunella vulgaris), as documented by J. Dupont in 2013. In addition to nutrition, the nectar of flowering forbs provide a source of water, which is necessary to avoid desiccation, as noted by Dana in 2013.

Larval Food Plants

Recent observations show that the preferred larval food plant for some populations of Poweshiek skipperling is prairie dropseed (Sporobolus heterolepis); zoo rearing programs feed larvae prairie dropseed, as documented by E.C. Runquist and others in 2020. For more information on larval food, refer to the 2014 listing rule and the 2015 critical habitat designation.

Poweshiek skipperlings are not known to disperse widely, with an estimated maximum dispersal distance of about 0.6 miles (1 kilometer) between patches of prairie habitat separated by structurally similar habitats, for example, perennial grasslands, but not necessarily native prairie, as noted by R. Westwood in 2012, as well as Dana in 2012. Dispersal of Poweshiek skipperling is very limited due in part to its short adult life span and single annual flight.

A recent observational study in Manitoba showed that Poweshiek skipperlings were observed ovipositing and then feeding on big bluestem, little bluestem, prairie dropseed and mat muhly grasses, as documented by J. Henault and R. Westwood in 2019. In 2017, Poweshiek skipperlings were observed oviposition on four different plant species in Michigan, although only one was a grass species, mat muhly, as documented by M.W. Belitz and others in 2019.

In 2013, Dana noted that larvae seem to need to begin feeding at a very fine, threadlike blade tip and females placed eggs on a fine blade tips of grasses during some observed ovipositions. Consistent with field observations of female oviposition on fine blades of grass, captively-reared caterpillars in early instars preferred feeding on finer leaf blades, as documented by Runquist in 2013.

In addition to using vegetation for oviposition and larval host plants, adult male Poweshiek skipperling may perch on tall grasses and forbs and appear to patrol in search of mating opportunities, as noted by R.A. Royer and G.M. Marrone in 1992. In Minnesota, the Poweshiek skipperling was observed almost exclusively as a patroller, noted Dana in 2013.