Orange Sulphur (Colias eurytheme) (Boisduval, 1852)
Diagnosis: The male of this species is bright orange above with a golden blush and solid black borders, or may be mainly yellow with an orange flush in the middle of the wings (see Remarks below). The female has yellow spots in the borders. White females are commonly encountered. There is a black spot in the forewing cell and a bright orange spot on the hindwing. The underside is similar to that of the Clouded Sulphur (C. philodice). Wingspan: 34 to 55 mm.
Range: This is a very common butterfly throughout the southern U.S., ranging north well into Canada. It is found in all provinces, but not in Yukon, the Northwest Territories or Nunavut. In British Columbia, it flies mainly in the south (e.g., the lower Fraser Valley) and in the Peace River District. There are no records for Labrador and only two from northern Quebec, at Rupert House and Kuujjuarapik (Great Whale River).
Similar Species: The Clouded Sulphur. In the Prairie Provinces the Orange Sulphur is most likely to be confused with the Christina Sulphur, but in eurytheme the orange on the upper surface extends to the wing base. In christina the basal quarter of the wings is yellow, the hindwing beneath has the dark submarginal spots reduced or absent, and the discal spot has a single red rim, usually without a satellite spot. Some specimens look intermediate and may be hybrids. [compare images]
Early Stages: Similar to those of the Clouded Sulphur.
Abundance: In southern areas (e.g., southern Ontario and southern Manitoba), it can be abundant in alfalfa fields. At Ottawa, it is always less common than Clouded Sulphur (C. philodice) and tends to fluctuate in numbers from year to year (Layberry et al., 1982).
Flight Season: There are two, possibly three, broods in Canada, with adults on the wing from May into November in southern Canada.
Habits: These are similar to the Clouded Sulphur and the two often mix with each other at mud puddles.
Remarks: Both this species and Clouded Sulphur (C. philodice) can become numerous enough in clover and alfalfa fields to be considered an agricultural pest. Cooler temperatures and shorter day length in the spring affect both larvae and pupae and result in a spring and early summer form of adults that are smaller, have narrower black borders, and orange shading reduced to an orange flush in the middle of the wings. At one time these forms were thought to be hybrids with philodice; the two species do hybridize, but only under unusual circumstances.
© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.
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