Butterflies and Moths of North America

collecting and sharing data about Lepidoptera

Western White
Pontia occidentalis (Reakirt, 1866)


Family: Pieridae
Subfamily: Pierinae
Identification: Upperside of forewing has marginal markings that are lighter than the submarginal stripe. Below, forewing tip and hindwing have veins outlined with gray-green. Short-day spring and fall forms have more prominent markings.
Wing Span: 1 1/2 - 2 1/8 inches (3.8 - 5.3 cm).
Life History: Males patrol hilltops and ridges for receptive females. Females lay eggs singly on host plants. Caterpillars will feed on leaves but prefer buds, flowers, and fruits. Chrysalids hibernate.
Flight: One flight from June-July in far north; two flights from May-August in the south.
Caterpillar Hosts: Flowers and fruits of various members of the mustard (Brassicaceae) family.
Adult Food: Flower nectar.
Habitat: Mountain peaks, slopes, hilltops, railroad yards, open plains, roadsides.
Range: Alaska south to central California, northern Arizona and northern New Mexico; east to North Dakota and central Ontario.
Conservation: Not usually required.
NCGR: G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.
Management Needs: None noted.
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