Atalopedes campestris

Atalopedes campestris (called sachem in the United States and Canada) is a small grass skipper butterfly.[2] It has a wingspan of 35–41 mm (1 3⁄8–1 5⁄8 in). Male is orange, edged with brown, and has a large brown-black stigma. Female is darker with lighter markings in the center of the wing.

Atalopedes campestris
Female

Secure  (NatureServe)[1]
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Hesperiidae
Genus: Atalopedes
Species:
A. campestris
Binomial name
Atalopedes campestris
Boisduval, 1852
  Year round
  Migration

Description

The sachem's wingspan is 35–41 mm (1 3⁄8–1 5⁄8 in).[3] The sexes are dissimilar but both have elongated wings.[4] The uppersides of the male forewing are orange bordered with brown and have a large four sided black stigma.[3] The color of the uppersides of the female wings are dark brown with golden spots in the center but are highly variable, light to very dark.[3] The uppersides of the female forewing have a black median spot and several semi-transparent spots.[4] Females can always be identified by the square white transparent spot at the end of the forewing cell.[3]

Underside of wings on both sexes are variable but the female hindwing is brown with light colored four-sided spots.[3]

The sachem is often mistaken for other skipper butterflies in the genus Hesperia.[5]

  • Female
  • Female
  • Male
  • Mating (female on left)

Distribution and habitat

This skipper is common in the southern United States ranging south through Mexico and Central America to Colombia, Venezuela, Ecuador, and Brazil.[3][6] During the warmer North American months, it can be found in northern parts of North America up to Montana, Washington, and New York excluding most of the Rocky Mountains.[7] One was sighted and photographed in southern Manitoba, Canada, on July 11, 2015.[8] Strays have been reported in British Columbia, Canada, three times, once each in 1937, 1953, and 1960.[2]

Atalopedes campestris can be found in open, disturbed areas such as roadsides, lawns, pastures, parks, oil fields, and landfills.[3][4]

It had been observed that the sachem expanded its range northward rapidly during the beginning of the 21st century. A study by Crozier shows that this expansion is due to the winter warming trend of climate change rather than evolution of cold tolerance for this species.[9]

Life cycle

The sachem butterfly undergoes fours stages of complete metamorphosis:

Eggs

Eggs are greenish-white and are laid singly on or near the host plant leaves.[7] The height of the egg is 0.9–1.0 mm (1⁄32–3⁄64 in). The width of the egg is 0.6–0.7 mm (1⁄48–1⁄32 in). The egg has polygonal sculpturing on its surface.[10]

Larvae

The Atalopedes campestris larva (or caterpillar) goes through five stages called instars.[10] Each caterpillar must shed its exoskeleton in order to grow. Differences between instars can be seen in altered body proportions, colors, patterns, changes in the number of body segments, or head width.

Larvae of the Family Hesperiidae "have a head, three thoracic segments, and ten abdominal segments." Each segment in the thorax has a pair of true legs. Segments three to six and ten in the abdomen have prolegs. Respiration openings, called spiracles, can be found on the first segment of the thorax and segments one to eight of the abdomen.[10]

The last abdominal segment, segment ten, features an anal comb. The anal comb is shaped like a fan and located near the anus to launch the caterpillar excrement, or frass, away from the caterpillar. Sometimes the frass is propelled several feet away.[10]

The sachem caterpillar's head is black.[4] Its body is dark olive green with black dots or bumps and a dark dorsal line.[7][3] The legs are brown. The length of the larvae in the last instar varies from 18 to 40 mm (3⁄4 to 1 5⁄8 in).[10]

The larvae construct nests made of a host plant leaf (or leaves) and silk that they excrete. They build new shelters as they grow and move through their different instars.[11] The larvae spend most of their lives in these shelters.[7]

Pupa

The sachem larva pupates in the same silked-leaf nest where it spends most of its life.[7]

The pupa is dark brown, almost black[7] and is cream colored on the end of the abdomen which has brown dots.[10] The proboscis extends 2 mm (5⁄64 in) beyond the wings.[7] The length of the pupa is 18.0–22.5 mm (23⁄32–7⁄8 in) with a width of 4.30–5.83 mm (1⁄8–1⁄4 in).[10]

The pupae of hesperiid have the same basic structure as the larvae—a head, three thoracic segments, and ten abdominal segments. The last abdominal segment is modified into the cremaster which is used to cement the pupa to the nest. Before an adult butterfly emerges from the pupa, the legs, wing, and antennae of the butterfly can be seen in the pupa; these are cemented to the body.[10]

Adult

An adult butterfly emerges from the pupa. The time that adult sachems take flight, mate, and the female lays fertilized eggs is known as a flight. This happens three times, May through November, in the northern part of their range. In the southern part of their range, flights occur four to five times, March through December.[3] Males perch on grasses during the day to await females. Migration occurs to the north and only one mass migration is known to occur in late summer.[7]

Larval host plants

The host plants used by the sachem caterpillar are various grasses including Bermuda grass, hairy crabgrass, red fescue, St. Augustine grass, Indian goosegrass,[7] seashore saltgrass, and Imperata cylindrica.[10]

  • Bermuda grass (Cynodon dactylon)
  • Crab grass (Digitaria sanguinalis)
  • red fescue (Festuca rubra)
  • St. Augustine grass (Stenotaphrum secundatum)
  • Indian goosegrass (Eleusine indica)
  • seashore saltgrass (Distichlis spicata)
  • Imperata cylindrica

References
  1. "NatureServe Explorer 2.0 Atalopedes campestris Sachem". explorer.natureserve.org. Retrieved 27 September 2020.
  2. Shepard, John; Crispin Guppy (2001). Butterflies of British Columbia: Including Western Alberta, Southern Yukon, the Alaska Panhandle, Washington, Northern Oregon, Northern Idaho, and Northwestern Montana. UBC Press. p. 114. ISBN 978-0-77480-809-5.
  3. Opler, Paul A.; Vichai Malikul (1998). A Field Guide to Eastern Butterflies (Peterson Field Guides). Houghton Mifflin Company. p. 380. ISBN 978-0-395-90453-4.
  4. Daniels, Jaret C. (2003). Butterflies of Florida Field Guide. Adventure Publications, Inc. pp. 184–185. ISBN 978-1-59193-005-1.
  5. Brock, Jim P.; Kaufman, Kenn (2003). Kaufman Focus Guides Butterflies of North America. New York: Houghton Mifflin Company. p. 302. ISBN 978-0618254002.
  6. "FAMILIA HESPERIIDAE". Bio-Nica.info - Su portal web sobre la Biodiversidad de Nicaragua (in Spanish). Retrieved 10 September 2018.
  7. Scott, James A. (1986). The Butterflies of North America A Natural History and Field Guide. Stanford University Press. p. 448. ISBN 978-0-8047-2013-7.
  8. "Sighting 1054222". Butterflies and Moths of North America. Retrieved 10 September 2018.
  9. Crozier, Lisa (2003). "Winter Warming Facilitates Range Expansion: Cold Tolerance of the Butterfly Atalopedes Campestris". Oecologia. 135 (4): 648–656. doi:10.1007/s00442-003-1219-2. JSTOR 4223634. PMID 12684862. S2CID 6679111.
  10. Minno, Marc C. (1994). Immature stages of the skipper butterflies (Lepidoptera: hesperiidae) of the United States : biology, morphology, and descriptions (PhD). University of Florida. pp. 27, 268–269. Retrieved 2018-09-11.
  11. Lind, Eric M.; Jones, Meg T.; Long, Jeremy D.; Weiss, Martha R. (2001). "Ontogenetic Changes in Leaf Shelter Construction by Larvae of Epargyreus Clarus (Hesperiiddae), The Silver-spotted Skipper" (PDF). Journal of the Lepidopterists' Society. 54 (3). Retrieved 15 September 2018.
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