Skippers: Poweshiek skipperling (Oarisma poweshiek)

(Lepidoptera: Hesperiidae: Hesperiinae)

Profile prepared by Matthew Shepherd, The Xerces Society

As with other prairie-dependent species, the Poweshiek skipperling has been in severe decline as the prairies have been destroyed. The historic range was from Manitoba to Iowa, with disjunct fen popluations in parts of Michigan, Minnesota, and Wisconsin; however, it is now much reduced due to conversion and fragmentation of the prairies. Threats include agricultural conversion of prairie, degradation of prairie due to grazing and haying, invasive weeds and neglect, and poor fire management. The latter is a key issue on many prairies now managed for wildlife.

red list profile

conservation status

Xerces Red List Status: Imperiled
Other Rankings:

Canada – Species at Risk Act: Threatened
Canada – provincial status: None
Mexico: N/A
USA – Endangered Species Act: None
USA – state status: WI: Endangered
IA, MI: Threatened
MN: Species of Concern
NatureServe: G2G3
IUCN Red List: N/A

As with other prairie-dependent species, the Poweshiek skipperling has been in severe decline as the prairies have been destroyed. It was probably once frequent across the landscape but now confined to a small number of scattered locations. With prairie fragmentation, populations have become isolated and some of the smaller and more isolated ones will likely not persist.

In Canada, the Poweshiek skipperling is listed at the federal level as threatened by COSEWIC. In the U.S., there is no federal protection but it is listed as endangered by Wisconsin, as threatened by Iowa and Michigan, and it is a species of concern in Minnestoa.

description and taxonomic status


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The Poweshiek skipperling is a small butterfly in the family Hesperiidae (skippers). Its wingspan is 1 to 1¼ inches (2.5 to 3.2 cm).

The upperside of the wings is very dark brown (often appearing black) with orange overscaling along the front edge of the forewing and along the veins. The underside of the wings is also dark brown (black), with orange along the front margin and a distinctive pale area on the hindwing, within which the veins are white.

Oarisma poweshiek (Parker), 1870. Common names include Hespérie de Poweshiek.

life history

The Poweshiek skipperling is an obligate resident of undisturbed tall- grass prairies. It is often associated with wetter prairies (for example, alkaline fens in Michigan and wet prairie in Manitoba), but it is possible that this is because dry areas are rendered unsuitable by too- frequent fires rather than a preference for wet areas. The larval hostplant is generally slender spike rush (Eleocharis elliptica), but in Wisconsin it is reported to feed primarily on prairie dropseed (Sporobolis heterolepis) and little bluestem (Schizachyrium scoparium).

There is one brood between June and August. Males seek females by patrolling close to the ground. Females lay eggs singly on leaves of hostplants. Caterpillars hibernate as fifth instar larvae.

Abundant nectar is an important requirement for adult skippers. Poweshiek skipperlings drink nectar from a range of flowers, including black-eyed Susans (Rudbeckia sp.), purple coneflower (Echinacea sp.), ox-eye daisy (Leucanthemum vulgare), and stiffleaved coreopsis (Coreopsis).

distribution

The historic range was from Manitoba to Iowa, with disjunct fen popluations in parts of Michigan, Minnesota, and Wisconsin. Now the range is much reduced to one area in both Michigan and Iowa, several sites in western Minnesota, Wisconsin, and the Dakotas, and a single metapopulation in Manitoba. It is probably extirpated from Illinois.


Courtesy of Butterflies and Moths of North America, Big Sky Institute.

threats and conservation needs

Threats

The Poweshiek skipperling is a prairie-dependent butterfly, and massive loss of prairies has been the biggest cause of its decline. It is estimated that since the 1850s, over 99 percent of its tall- grass prairie habitat has been converted to agricultural uses; for example, in Canada, only about 50 km2 of the original 6,000 km2 of tall- grass prairie remains.

The loss, fragmentation, and degradation of the remaining prairie continues to be the principle threats. Conversion of prairie to row crops is an obvious threat: the wild flowers that survive do not represent enough of the prairie flora to support the skipperling. Conversion of the prairie to grazing may be less obvious but not less of a threat. Grazing will alter the species and structural diversity of the grassland and the associated use of herbicides and fertilizers can impoverish the flora. Use of prairie for haying can also impact the butterflies depending on timing of operations.

Even when prairie is protected as wildlife habitat it may not provide a safe haven for the Poweshiek skipperling and other prairie-dependent butterflies such as the ottoe skipper (Hesperia ottoe; see Red List profile for more information). Prescribed burns can severely impact butterfly populations when it is done too frequently or over too great of an area. Similarly, neglect of the prairie can impact butterflies by allowing scrub to develop or for exotic weeds to invade. Purple loosestrife (Lythrum salicaria) is potentially a major threat to wet prairie habitats, for example.

Conservation needs

The major need is protection and appropriate management of remaining prairie wherever this butterfly is found. The Poweshiek skipperling is very susceptible to disturbance or alteration of its habitats. It is important that habitat supports both adult and larval food plants, plants that rarely occur in agricultural lands.

Fire is a key issue for this butterfly. Too-frequent, ill-timed fires can severely impact populations, as can burning too much of the habitat at one time. It is likely that fires of less than three- or five-year frequencies can result in extirpation of the Poweshiek skipperling from a site. The Wisconsin Department of Natural Resources notes: “The Powesheik skipperling is fire-sensitive and burn management used to discourage woody plants and cool-season grasses in the open wet prairie community is best conducted with controlled infrequent burns affecting only a portion of the available habitat. Selective cutting and mowing may be better management tools for inhabited patches.”

Surveys of suitable habitat to inventory known populations and locate new ones are important. Monitoring of populations to track status and trends would be useful. Studies into the impacts of fire, including the ability of the skipperling to recolonize burned areas would be valuable.

references

COSEWIC. 2003. COSEWIC assessment and status report on the Poweshiek skipperling Oarisma poweshiek in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 25 pp. (Available online; Accessed 10/29/13.)

Opler, P. A., and G. O. Krizek. 1984. Butterflies East of the Great Plains. Johns Hopkins University Press, Baltimore, MD.

Opler, P. A., and V. Malikul. 1992. A Field Guide to Eastern Butterflies. Peterson Field Guide #4. Houghton-Mifflin Co., Boston, MA.

Scott, J. A. 1986. The Butterflies of North America. Stanford University Press, Stanford, CA.

Stanford, R. E., and P. A. Opler. 1993. Atlas of Western USA Butterflies Including Adjacent Parts of Canada and Mexico. Denver and Fort Collins, CO.

Tilden, J. W. 1986. A Field Guide to Western Butterflies. Houghton-Mifflin Co., Boston, MA.

additional resources

Big Sky Institute, Butterflies and Moths of North America: Poweshiek skipperling (Accessed 1/21/09)

Government of Canada, Species at Risk Act Public Registry; Species Profile: Poweshiek skipperling (Accessed 5/11/05)

Committee on the Status of Wildlife in Canada (COSEWIC); Status Report: Poweshiek skipperling (Accessed 5/11/05)

Canadian Biodiversity Information Facility; Species Bank: Poweshiek skipperling (Accessed 5/11/05)

The poweshiek skipper project (Accessed 1/30/09)

Wisconsin Department of Natural Resources; Wisconsin’s Threatened & Endangered Butterflies & Moths: Poweshiek skipperling (Accessed 10/29/13)

NatureServe Explorer (Accessed 9/23/08)

citation

Shepherd, M. D. 2005. Species Profile: Oarisma poweshiek. 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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