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Hesperia uncas

By Courtney Christensen

Geographic Range

The Uncas skipper, Hesperia uncas, ranges across Canada from Saskatchewan to Alberta, and down into the United States through the Rocky Mountains and Great Plains. From the Great Plains its range extends south to Texas and New Mexico.

There are two isolated populations, one in south central Mexico and the other in Minnesota. In Minnesota, a small population only exists in the sand dunes of Sherburne County. This population is 500 kilometers east of its known limits in the Dakotas. This population in Minnesota is different, phenotypically, than that of the population in the Great Plains. Two recent sightings of H. uncas males in southwestern Minnesota might indicate a wider distribution in the eastern side of South Dakota, however lack of habitat in this area would likely prevent the establishment of a population. (Coffin and Pfannmuller, 1988)

Habitat

Uncas skippers can primarily be found in both alkaline and short grasslands, as well as grassy alkaline flats. Some western populations appear commonly clustered on thistles in southwestern road ditches by the dozens. Uncas skippers in California are located at higher elevations in the White Mountains of Mono and Inyo. (Brock, 2003; Garth and Tilden, 1986; Glassberg, 2001)

  • Range elevation
    989 to 8100 m
    3244.75 to 26574.80 ft
  • Average elevation
    5500 m
    18044.62 ft

Physical Description

The Uncas skipper is very similar to other skippers that it flies with, but this butterfly is small at 28 to 34 mm long, with a robust body, angled forewings, and shorter, more round hind wings. Its wingspan averages 3.1 to 3.81 cm. On the underside of its wings, the Uncas skipper has extensive hindwings of white chevron with connected spots, with white veins and blotchy dark brown to black markings. The white spots orientate inwardly and outwardly by dark green shades. The populations located in Mono County, California have reduced hindwing white veining and often have dark brown to black markings. Like all skippers, Uncas skippers have antennas that are relatively short which have clubbed ends and tips that curve backwards.

Males and females differ greatly on the upper side of the wings. Males will typically have a brownish orange darker coloration. Small light colored spots can be seen near the forewing tips. Males also have a linear black band of scent scales that are used in courtship. These scales are placed on the long axis of the forewings. Females tend to be darker, with larger white spots on the forewings. Uncas females tend to have larger, and more broad wings which is a characteristic found in skippers. Both sexes will become duller with age as the scales fall off, but the pattern will never disappear.

The eggs appear greenish white and are hemispherical. The young larvae form is pale brown, and the head is a darker brown with cream spots and streaks in the front. ("Hesperia uncas", 2014; Coffin and Pfannmuller, 1988; Glassberg, 2001; "Hesperia uncas", 2014; Opler, 1999)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • ornamentation
  • Range length
    28 to 34 mm
    1.10 to 1.34 in
  • Range wingspan
    3.3 to 3.81 cm
    1.30 to 1.50 in

Development

Pupae emerge during the spring or summer, depending on the region. In South Dakota and much of its range, H. uncas has two generations, one in May and June, the other in July to September. In Minnesota, it has only one generation in June and July. After emerging from pupation, adults take flight and find mates. Eggs are laid, and hatch after about 10 days. In the first generation, larvae go through several instar stages, pupate, and then emerge as adults. In the second generation (or for the only generation in Minnesota), larvae develop until the fourth or fifth instar, and then go into hibernation for the winter. They emerge again in late spring or summer, and pupate for 2 to 3 weeks before emerging as adults and beginning the cycle again. ("Hesperia uncas", 2014)

Reproduction

Based on similar species in the genus, female Uncas skippers probably mate shortly after emergence and will rarely remate. The males will look for receptive females by perching on low vegetation or directly on bare sand. Males use the scent scales on their wings to produce pheromones for courtship. Many males will also collect on hills or ridges, which may draw the attention of females, though little is known for sure about this behavior. Receptive females respond to males by descending into the vegetation where mating follows. ("Hesperia uncas", 2014)

Depending on the area, Uncas skippers can have one or two generations per year. In South Dakota and most of its range, there are two generation per year, with adults present from May to June and July to September. In Minnesota, there is one generation per year from June to July. After mating, the female finds plants to oviposit on; all observed ovipositions of H. uncas have been made on hairy grama (Boutelous hirsute), which is a tufted grass. The female will lay only a single egg before moving on to the next tuft. (Glassberg, 2001; "Hesperia uncas", 2014)

  • Breeding interval
    Females mate once in their lives, while males will mate as much as possible.
  • Breeding season
    Depending on the region, mating takes place from late spring to late summer.

Females provide provisioning in their eggs, as well as lay the eggs on suitable host plants for the larvae to feed upon hatching. After the eggs are laid, there is no more interaction or care by the parents. ("Hesperia uncas", 2014)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

Adults of Hesperia uncas likely live for about 3 weeks after emerging from pupation. ("Hesperia uncas", 2014)

  • Average lifespan
    Status: wild
    21 days

Behavior

The larvae will live in shelters that grow in size, that they themselves built out of silk and plant materials. The shelters are built bigger and bigger as the larvae grow too. Overwintering larvae have also been found in shelters that have been build under the soil. Adult Uncas skippers are very rapid and strong fliers. They have a very fast wing beat that almost appears to be like a blur to human eyes. ("Hesperia uncas", 2014)

Communication and Perception

Male Uncas skippers have a linear black band of scent scales on their wings that release pheromones during courtship. Males also may communicate with females visually, as the males collect in groups on high ridges before females, likely a visual cue to females. ("Hesperia uncas", 2014)

Food Habits

The larval food source for Uncas skipper is blue grama (Bouteloua gracilis) grass and other grasses such as hairy grama (Bouteloua hirsute). Uncas skipper adults seek nectar and will feed from almost any flowers available, but golden aster (Heterotheca villosa) and hairy puccoon (Lithospermum caroliniense) are the preferred sources of nectar. (Coffin and Pfannmuller, 1988; "Hesperia uncas", 2014)

  • Plant Foods
  • leaves
  • nectar

Predation

There is no information available about the predators of Hesperia uncas. As quick fliers, they are likely able to evade any ground predators, as well as many airborne predators. ("Hesperia uncas", 2014)

Ecosystem Roles

Uncas skippers, like other butterflies and moths feed on flowers nectar and therefore help contribute to pollination of plants. ("Hesperia uncas", 2014)

  • Ecosystem Impact
  • pollinates

Economic Importance for Humans: Positive

There are no known positive effects of Hesperia uncas on humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Hesperia uncas on humans.

Conservation Status

Under the Minnesota's List of Endangered, Threatened, and Special Concern Species, Hersperia uncas is listed as endangered. This is due to the destruction of its habitat in that state, and only a small population in an isolated area remains there. Conservation efforts are underway to protect the population and its habitat in this area.

On a national level, Hesperia uncas has no special conservation status. ("Hesperia uncas", 2014)

Contributors

Courtney Christensen (author), Minnesota State University Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Angela Miner (editor), Animal Diversity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diapause

a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

suburban

living in residential areas on the outskirts of large cities or towns.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Minnesota Department of Natural Resources. 2014. "Hesperia uncas" (On-line). Species Profile: Minnesota DNR. Accessed April 16, 2014 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=IILEP65010.

Brock, J. 2003. Kaufman Field Guide to Butterflies of North America. New York, United States of America: Houghton Mifflin Company.

Coffin, B., L. Pfannmuller. 1988. Minnesota's Endangered Flora and Fauna. Canada: University of Minnesota Press. Accessed March 26, 2014 at http://mnsu.summon.serialssolutions.com/?s.q=uncas+skipper#!/search?ho=t&q=uncas%20skipper&l=en.

Garth, J., J. Tilden. 1986. California Butterflies. United States of America: University of California Press.

Glassberg, J. 2001. Butterflies Through Binoculars. New York, United States of America: Oxford University Press, Inc..

Holland, J. 2003. Field Guide to Butterflies. Canada: Sterling Publishing Co, Inc..

Opler, P. 1999. A Field Guide to Western Butterflies. New York: Houghton Mifflin Company. Accessed April 21, 2004 at http://books.google.com/books?id=ilL_XX1rbNoC&pg=RA2-PT360&dq=Holland+field+guide+to+butterflies&hl=en&sa=X&ei=MeJVU5y7HNGKyATKjYKIAw&ved=0CEQQ6AEwAg#v=onepage&q=uncas%20skipper&f=false.

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