California Tortoiseshell (Nymphalis californica) (Boisduval, 1852)

Diagnosis: This species is smaller (wingspan: 45 to 61 mm) than the Compton Tortoiseshell (N. vaualbum). The upperside is dark orange with black spots and a black margin. The underside is mottled brown, darker towards the base. There are blue marks near the margin of the hindwings. Unlike the similar anglewings, there is no silver mark on the underside of the hindwings.

Subspecies: Subspecies herri is the one that occurs in the Canadian part of its range.

Range: Mainly a western U.S. species, this butterfly is resident in Canada only in southern British Columbia north to Rainbow Mountain in Tweedsmuir Provincial Park, and in southwestern Alberta. In years of abundance, strays have been found farther north in Alberta, in southern Saskatchewan, and in southwestern Manitoba. In the U.S. it has been recorded as far east as New York and Vermont and could reach southwest Ontario during good migrant years.

Specimen collection data

Similar Species: The only similar species is the Compton Tortoiseshell. [compare images]

Early Stages: The black larvae have a pale line down the back and black branched spines with blue at the base. They feed on various Ceanothus species; in BC it is recorded on Redroot (Ceanothus sanguineus) (Jones, 1951).

Abundance: In British Columbia this can be a common butterfly. In some years in the west, it builds up in numbers and large migrations take place. This is when strays can occur just about anywhere in the west and even occasionally in the east.

Flight Season: There is a single generation that emerges in July or August and overwinters to the next spring. East of Alberta, migrants are usually seen in August or September.

Habits: It is usually found in forested areas in the mountains, particularly in glades or canyons.

© 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.