Field Crescent (Phyciodes pratensis) (Behr, 1863)
Diagnosis: This small crescent (wingspan: 24 to 36 mm) appears to be mainly black with pale orange markings on the upperside. The median band on the forewing is made up of separate discontinuous spots and the light bar in the cell on the forewing is distinct from other light markings. The underside is yellow with rusty patches and the black marks on the underside of the forewing are small and indistinct.
Subspecies: The nominate subspecies occurs over most of the Canadian range from the Rocky Mountains west. Subspecies camillus, which has a slightly more patterned underside, has been named from southern Alberta populations but it is not very distinctive.
Range: Widespread in the west from the Mexican border to central Alaska, this is mainly a mountain species in western Canada. It ranges from the U.S. border north through British Columbia, western Alberta, and Yukon almost to the Arctic Ocean at Aklavik, Northwest Territories. Specimens from the Cypress Hills of Saskatchewan have been re-identified as Phyciodes batesii.
Similar Species: Best distinguished from the five similar Phyciodes in Canada by the dark upper surface and by the transverse light bar on the forewing cell near the middle of the wing on the underside.
Early Stages: The black larvae have spines with orange at the base. As with the other crescents they feed on a variety of asters (Aster spp.).
Abundance: The Field Crescent is fairly common throughout its range.
Flight Season: Single-brooded, pratensis flies from late May into August in its Canadian range.
Habits: This species is wide-ranging in its habitat preferences from fields and roadsides to woodland clearings in mountainous and hilly country.
Remarks: Some authors have used the name campestris (Behr) for this species. More recently the name Phyciodes pulchella (Boisduval) has been used (Scott, 1994; Bird et al., 1995). The name "Melitaea pulchella" lacked a description (required for all new species), but was proposed by Boisduval to be applied to an illustration of Phyciodes tharos in Drury's classical book (1773) that Boisduval believed represented the California species that later became known as pratensis. The name pulchella, however, must technically be considered a synonym of tharos as illustrated by Drury and cannot be applied to the Californian species that Boisduval had in mind.
© 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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