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| Pontia occidentalis (Reakirt, 1866) |
| Status: Rare to uncommon resident. |
| Flight Period(s): Data from Nebraska, where adults have been reported from 18 May to 21 August, indicate this species is probably triple brooded. In South Dakota the Western White has been reported from 23 April to 4 September (Marrone, 2002) and Scott (1986) reports three broods from the high plains of eastern Colorado, the latter brood flying in August and September. |
| Range: This species is a resident from much of Alaska east through Ontario, and south through Colorado, Utah, Nevada and northern California. In Nebraska it has been found in the panhandle and Dundy County. |
| Larval Hostplant(s): Various members of the Crucifer family are listed, of which the following occur in Nebreaska: Mustards (Arabis drummondi, A. glabra, Brassica nigra, Chorispora tennilla, Sisymbrium altissimum), Flixweed (Descurainia sophia), and varities of Peppergrasses (Lepidium virginicum and L. densiflorum). |
| Overwinter: As pupae. |
| Commentary/Habitat: The Western White is most often encountered on rocky or short grass prairie hillsides, although it has also been found in “urban” areas. It is being reported with increasing frequency in recent years (having first been found in 1977 by Franklin Snocker) with almost all Nebraska records having been gathered since the mid 1980s. Opler (1999) reports this species is expanding its range eastward in the northern United States and southern Canada, so it is possible this species is recently new to the state. However it is also likely that this species was often overlooked as being Checkered Whites. Due to these similarities all records of Western Whites should be verified by taking a specimen or two. In Nebraska the Western White has been found at Lake Minatare and Buffalo Creek State Wildlife Management Area (Scotts Bluff County), the I-80 East rest area west of Sidney (Cheyenne County), Gilbert-Baker State Wildlife Management Area (Sioux County), and in Chappell (Deuel County). |
| Similar Species: Checkered, Spring and Cabbage Whites. |
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