Description 1 1/8-1 3/8" FW slightly indented along outer margin.
Above, orange with open pattern of fine black lines. Beneath, FW orange
with dark lines and spots and small black spot on trailing margin; HW has
yellowish-brown areas, white bands, and white marginal crescent in brown
Life Cycle Egg cream-colored; laid in clusters. Caterpillar overwinters
half grown; mature caterpillar to 7/8" black with yellowish stripes and
spots; many branching spines. Host plants are thistles, mild thistle, and
plumeless thistle. Chrysalis, to 3/8", mottled brown to gray with golden
sheen and tubercles.
Flight Several overlapping broods; March-October.
Habitat Agricultural fields, dry canyons, mountains, open woods,
shorelines, marshes, vacant lots, meadows, and roadsides.
Range British Columbia and Montana south to Baja California, New
Mexico, and S. Mexico.
Discussion In the 1800's weedy thistles spread all over the West and
were followed by the Mylitta Crescent. Now this species seems ubiquitous
and is found in many disturbed as well as natural habitats. Flying from
early spring to autumn, it is most abundant in August. Individual butterflies
tend to occupy the same territories or stands of nectar flowers for several
days at a time.