Checkered White (Pontia protodice) (Boisduval and Le Conte, 1830)
Diagnosis: A medium-sized species that resembles the other species in the genus Pontia. The male has a dark brown checkered pattern around the edge of the forewing upperside; on the hindwing the upperside is a clear white, while the underside has few or no markings. The female is more heavily checkered on the upperside than the male. There is a great deal of variation, particularly in the darker forms that occur in the spring and fall. Wingspan: 33 to 49 mm.
Range: This widespread butterfly is found in the southern U.S. from the Atlantic to the Pacific as a permanent resident. In the northern U.S. and southern Canada it appears sporadically, setting up temporary colonies that may last the summer, or for several years. There are only a few records from Quebec, one near Montreal and another northwest of Hull. In Ontario, some colonies have persisted for several years, as far north as the Ottawa Valley and Sault Ste. Marie. In the west, it is uncommon in southern Manitoba and across the southern Prairies to eastern British Columbia; it often occurs in company with the more numerous Western White. The most remarkable record was two specimens taken, and others seen, on September 10, 2001, by Cheryl Davis at Wabush, in extreme western Labrador, clearly the offspring of a female that had strayed about 1000 km further north than usual!
Similar Species: Males are unmistakable, with their much-reduced dark scaling. Females are often difficult to distinguish from those of the Western White (P. occidentalis). The dark markings of occidentalis tend to be more black, as opposed to brownish or grey, and the dark spot on the lower margin of the forewing underside is larger in protodice than in occidentalis. Even so, some females are difficult to identify by these features. There is a feature of the wing venation that separates about 80% of specimens with confidence (Chang, 1963). [compare images]
Early Stages: The larva is striped alternately in green and grey with many minute black tubercles. It feeds on a wide variety of members of the mustard family (Brassicaceae), including cultivated cabbage and turnip and many species of wild mustard. Hibernation is as a pupa.
Abundance: This white is not common in Canada. However, both the larvae and adults can be found regularly where it has temporarily established a colony.
Flight Season: Two flights have been recorded in Ontario, the first in June and July, the second in August and September. In Manitoba, it has been recorded from early July into September, becoming more frequent later in the summer.
Habits: Although widespread, the Checkered White tends to be found only in open disturbed habitats such as weedy fields, pastures, roadsides, and cultivated lands.
Remarks: The fluctuations in numbers of this species may have to do with the shifting nature of agriculture in North America. It has also been postulated that declining numbers in eastern North America may be the result of the extremely abundant Cabbage White expanding into the traditional range of other whites.
© 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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