Orange Sulphur

Colias eurytheme

Summary 6

The Orange Sulphur (Colias eurytheme), also known as the Alfalfa Butterfly and in its larval stage as Alfalfa Caterpillar, is a butterfly of the family Pieridae, where it belongs to the lowland group of "clouded yellows and sulphurs" subfamily Coliadinae. It is found throughout North America from southern Canada to Mexico, but is absent from the central and southeastern USA.

Description 6

Male Colias eurytheme hind wings demonstrate an ultraviolet reflectance pattern while female Colias eurytheme hind wings demonstrate ultraviolet absorbing patterns. According to studies, these ultraviolet reflecting wing scales found in males also contain pterin pigments that absorb wavelengths below 550 nm. Although this may seem paradoxical, the pterin pigments have been found decrease the amount of diffuse ultraviolet reflectance that comes from the wing scales. By suppressing the diffuse ultraviolet reflectance, the directionality and spectral purity of the iridescence is heightened. In addition, the presence of the pterin pigments increases the signal’s chromaticity and potential signal content, suggesting that these pigments are responsible for amplifying the contrast between ultraviolet reflectance and background colors as a male’s wings move during flight. Further studies have found that the ultraviolet reflectance signal is brightest within a wing beat cycle when viewed from directly above the male. This supports the idea that male wing color should be able to be readily distinguished from that of females and the visual background that consists mostly of UV-absorbing vegetation.

Larval Description 7

Mature larvae are dark, velvety green with a red-bordered, white lateral line with yellow to red dashes (Guppy & Shepard 2001).

Larval host plants 8

Plants in the pea family (Fabaceae) including alfalfa (Medicago sativa), white clover (Trifolium repens), and white sweet clover (Melilotus alba).

GTM Occurrence 8

The Orange Sulphur is rare at the GTM. Most observations were in the open habitat along Transect A with a single specimen spotted along the Marsh Pond Overlook (Transect B). Single specimens have been seen in April and August to November. There have been 5 specimens observed as of December 28, 2015.

Distribution 9

Colias eurytheme butterflies can be found from southern Mexico to almost all throughout North America. Historically, they were distributed primarily in the Nearctic regions of the west, but were displaced to the east by logging and alfalfa field planting.

Habitat 10

This species can be found in most any open area, including vacant lots, pastures, open fields, roadsides, and clover and alfalfa fields.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland

Other Habitat Features: urban ; suburban ; agricultural ; riparian

Nature serve conservation status 11

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread in lower 48 states and an abundant summer resident into Canada. Species has increased its range by about 40% since 1930. An occasional economic pest of alfalfa fields. This is one of the most common butterflies in the world and quite possibly the most common native butterfly in North America, and it increases each year as exotic legumes that the larvae do well on increase in the east and on top of that global warming can only increase its winter range, from which it colonizes much of the continent between June and September. The species is also somewhat migratory in the fall (Scott, 1986; Schweitzer, 2006) and part of the population emigrates from areas where it cannot survive the winter. Adults move north again in June.

Environmental Specificity: Broad. Generalist or community with all key requirements common.

Pest status 8

Larvae can be destructive in alfalfa fields.

Sources and Credits

  1. (c) Dan Mullen, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/8583446@N05/6137123754
  2. (c) TexasEagle, some rights reserved (CC BY-NC), https://www.flickr.com/photos/texaseagle/5103915220/
  3. (c) Vicki DeLoach, some rights reserved (CC BY-NC-ND), https://www.flickr.com/photos/vickisnature/2810244033/
  4. (c) TexasEagle, some rights reserved (CC BY-NC), https://www.flickr.com/photos/texaseagle/3587308600/
  5. (c) gtmresearchreserve, all rights reserved, uploaded by GTMResearchReserve, http://www.inaturalist.org/photos/2851754
  6. Adapted by GTMResearchReserve from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Colias_eurytheme
  7. Adapted by GTMResearchReserve from a work by (c) University of Alberta Museums, some rights reserved (CC BY-NC), http://eol.org/data_objects/31885502
  8. (c) GTMResearchReserve, some rights reserved (CC BY-SA)
  9. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Colias_eurytheme
  10. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31386969
  11. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28795061

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