Oarisma garita    (Reakirt, 1866)

Garita Skipperling 


MN Status:
threatened
Federal Status:
none
CITES:
none
USFS:
none

Group:
insect
Class:
Insecta
Order:
Lepidoptera
Family:
Hesperiidae
Habitats:

(Mouse over a habitat for definition)


Oarisma garita

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Map Interpretation

Map Interpretation

  Synonyms

  Basis for Listing

The Garita Skipperling, also known as the Garita Skipper, is a grassland species ranging from northern Mexico north through the Great Plains and Rocky Mountains to the Canadian parklands (Layberry et al. 1998; Opler et al. 2006). It reaches its eastern limit in southern Manitoba and northwestern Minnesota (although there is a disjunct population near Mantoulin Island in Ontario). Breeding colonies of the Garita Skipperling were discovered in the aspen parkland in Kittson County in the late 1980s (R. Dana, Minnesota DNR, pers. comm.), where colonies have been confirmed at three sites (Cuthrell 1991). There is also a record from the late 1960s from Clay County that may represent a brief, adventive establishment. All locations in Kittson County are in native prairie or savanna habitat on sandy soils. This habitat was always a minor landscape component in the region, and conversion of lands to crop production, overgrazing, aggregate mining, and succession to woodland have further reduced the amount.

This skipperling is dependent upon the survival of its native prairie habitat (Klassen et al. 1989). All three sites where the Garita Skipperling has been observed are substantially protected from destruction, but active management to prevent succession to woodland will be necessary. There is some unprotected habitat at all three sites that is vulnerable to destruction. A home was recently built in one of these unprotected areas. Other unprotected sites having potential habitat are under considerable threat. Isolation and small size of the remnant habitat makes all occurrences of garita skipper highly susceptible to extirpation. For these reasons, the Garita Skipperling was listed as a threatened species in Minnesota in 1996.

  Description

The Garita Skipperling is a small butterfly, smaller and more delicate looking than most other skippers in Minnesota. Forewing length (base to apex) is 1.1-1.3 cm (0.4-0.5 in.) in both sexes. Antennae are short and relatively stout and have blunt-tipped clubs. Though capable of rapid flight, this skipperling more typically flies erratically just above the grass tops at a speed that is relatively easy to follow with the eye. Its flight is somewhat mothlike and lacks the skipping quality that gives the family its name.

Males and females are similar in appearance as well as in size. On the upper side, the wings are a warm orange brown, with a golden sheen in fresh individuals. There are no distinct markings. Males do not have a brand on the forewing. Beneath, the ground color is orange, with the hind wing veins traced in lighter colored scales.

In Minnesota, the most similar species to the Garita Skipperling is the closely related Poweshiek Skipperling (Oarisma poweshiek). The Powesheik Skipperling is slightly larger and much darker above, almost black when fresh. Beneath, the hind wing ground color is grayish brown and the whitish veins contrast more strongly. The Poweshiek Skipperling flies later than the Garita Skipperling, although there is some overlap. The introduced European Skipper (Thymelicus lineola) is about the same size as the Garita Skipperling, but the wings are bright golden orange above with narrow dark margins. Beneath, the hind wing veins are not conspicuously lighter than the ground color.

  Habitat

Habitat for the Garita Skipperling in Manitoba is described as dry and moist virgin prairie, with hollows or bases of hills favored in dry prairie (Klassen et al. 1989). Dry prairie seems to be the preferred habitat in North Dakota, where the Poweshiek Skipperling occupies moister prairie (McCabe and Post 1977). In Minnesota, the Garita Skipperling has been observed in prairie openings on sandy soils, in either old dune formations or outwash deposits. In all cases, moister swales or hollows occur together with the drier hillocks or swells. Dominant grasses of the drier prairie include little bluestem (Schizachyrium scoparium var. scoparium), prairie junegrass (Koeleria macrantha), porcupine grass (Hesperostipa spartea), and needle-and-thread grass (S. comata). In one of these locations there are scattered small, gnarly bur oaks (Quercus macrocarpa).

  Biology / Life History

The Garita Skipperling has a single annual generation. All observations of this species in Minnesota have been in the first half of June, although the flight period probably extends somewhat into July, as it does in North Dakota and Manitoba (McCabe and Post 1977; Royer 1988; Klassen et al. 1989). It overwinters as a partly grown larva and completes development the following spring (Scott 1986).

Larval habits of the Garita Skipperling have not been described in detail. It feeds on grasses (possibly also on upland sedges), but preferences in Minnesota are not known. Scott (1986) reports several species, of which blue grama (Bouteloua gracilis) and Kentucky bluegrass (Poa pratensis) occur in Minnesota. Larvae do not build shelters (Bird et al. 1995). Adults regularly visit flowers for nectar (McCabe and Post 1977). Royer (1988) suggests a preference for flowers of legumes (Fabaceae).

Males seek mating opportunities through meandering search flights above and among the tops of the grasses, a behavior often known as patrolling, in contrast to the perch-chase behavior of many skippers (Scott 1986). Females probably mate soon after they become capable of flight, but how often they remate is not known. Life expectancy has not been reported, but it is unlikely to be more than a few days, possibly a week. Nothing is known about the dispersal behavior of mated females.

  Conservation / Management

Small colony sizes due to past habitat loss, and further habitat destruction are the primary threats facing the garita skipper in Minnesota. All habitat that is not protected by permanent dedication for conservation is at risk of destruction for agricultural production, aggregate mining, or development. Loss of the unprotected habitat at the sites where this skipperling is known to occur will make the colonies even more vulnerable. Extirpation could result from natural events (such as severe drought or hailstorms) or human caused ones (such as insecticide application), as well as from the vagaries of normal population processes (for example, by chance all adults in one generation are males). Loss of genetic diversity is another possible threat. Even where protected, the habitat in northwestern Minnesota is strongly susceptible to woodland invasion and requires active management intervention to maintain it.

The Garita Skipperling is probably highly sensitive to fall or spring prescribed burns, as larvae and pupae are likely to be exposed to lethal temperatures based on what is known about the Poweshiek skipperling (R. Dana, Minnesota DNR, pers. comm.). Even the lower energy output of fire in dry prairie would still be devastating to completely unconcealed larvae. Accordingly, the use of prescribed fire as a habitat management tool should be judicious. A site should be subdivided and the units burned in a rotation that leaves enough larval habitat unburned to assure population survival and recolonization of burned areas between burns. This may be difficult for small sites. Haying may provide a suitable option in these cases; Swengel (1998) provides evidence that late-summer haying is more favorable for several prairie skippers than rotational burning. Mowing should not occur until eggs have hatched (late July).

Several programs and resources are available to land managers and landowners to help protect and manage remaining prairie parcels including the Native Prairie Bank Program, the Native Prairie Tax Exemption Program, and a prairie restoration handbook.

  Conservation Efforts in Minnesota

Following the discovery of breeding colonies of the Garita Skipperling in Kittson County, the Minnesota DNR conducted a more intensive survey in the Tallgrass Aspen Parklands Province of northwestern Minnesota. All three locations found are substantially protected from destructive development: a Minnesota DNR Wildlife Management Areas, a State Park, and a Nature Conservancy preserve. No conservation efforts specifically targeted to this skipperling have been undertaken, however, prescribed burning at the Nature Conservacy site is conducted in accordance with guidelines that reduce risk to grassland insects. The other two sites have enough habitat that prescribed burning is not likely to extirpate the skipperling colonies. Additional survey work on this species is needed.

  References

Bird, C. D., G. J. Hilchie, N. G. Kondla, E. M. Pike, and F. A. H. Sperling. 1995. Alberta butterflies. The Provincial Museum of Alberta, Edmonton, Alberta. 349 pp.

Cuthrell, D. L. 1991. The butterflies of Kittson and Roseau counties, Minnesota, with special emphasis on the Dakota Skipper (Hesperia dacotae) [Skinner]. Final report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 48 pp.

Klassen, P., A. R. Westwood, W. B. Preston, and W. B. McKillop. 1989. The butterflies of Manitoba. Manitoba Museum of Man and Nature, Winnipeg, Manitoba. 290 pp.

Layberry, R. A., P. W. Hall, and J. D. LaFontaine. 1998. The butterflies of Canada. University of Toronto Press, Toronto, Ontario. 280 pp. + color plates.

McCabe, T. L., and R. L. Post. 1977. Skippers (Hesperioidea) of North Dakota. North Dakota Insects Publication No. 11, Schafer-Post Series. Agricultural Experiment Station, University of North Dakota, Fargo, North Dakota. 70 pp.

Opler, P. A., H. Pavulaan, R. E. Stanford, and M. Pogue, coordinators. 2006. Butterflies and moths of North America: Garita Skipperling (Oarisma garita). Bozeman, Montana: NBII Mountain Prairie Information Node. . Accessed 20 July 2006.

Royer, R. A. 1988. Butterflies of North Dakota: an atlas and guide. Science Monograph Number 1, Minot State University, Minot, North Dakota. 192 pp.

Scott, J. A. 1986. The butterflies of North America: a natural history and field guide. Stanford University Press, Stanford, California. 583 pp.

Swengel, A. B. 1998. Effects of management on butterfly abundance in tallgrass prairie and pine barrens. Biological Conservation 83(1):77-89.