Rocky Mountain Dotted Blue (Euphilotes ancilla) (Barnes & McDunnough, 1918)

Diagnosis: In the male the upperside is lilac blue, with narrow black margins and a trace of dark dots on the hindwing margin. The female is dark brown with a bluish sheen and an orange crescent near the hindwing margin. The underside is grey, with two rows of dark spots near the margin of both wings. There is a row of orange spots between them on the hindwing and many small round spots in the central area of both wings. Wingspan: 17 to 23 mm.

Subspecies: Only the nominate subspecies ancilla is found in Canada.

Range: Euphilotes ancilla is widely distributed in the western U.S., but occurs in Canada only in extreme southern Saskatchewan and Alberta, north to the Oldman River Valley in Alberta and to Matador in Saskatchewan.

Specimen collection data


Similar Species: The Square-spotted Blue (E. battoides). [compare images]

Early Stages: Eggs are laid singly on flowers, and larvae eat flowers and young fruit. The larvae vary in colour but are usually pale, whitish, or yellowish with brown markings, matching the colour of the flowers. They feed on various species of buckwheat (Eriogonum spp., probably E. flavum in Canada), and hibernate as pupae.

Abundance: One of the commonest blues in the western U.S., ancilla is very rare in Canada.

Flight Season: Adults are on the wing from mid-May to early July.

Habits: Euphilotes ancilla flies in open woodland, sagebrush, and dry prairies.

Remarks: The first Canadian specimen was taken by Ronald Hooper near Elkwater, in the Cypress Hills of eastern Alberta, on 18 June 1963. It has since been taken at several places in southern Saskatchewan and Alberta. Until recently ancilla was considered to be one of a large number of subspecies of Euphilotes enoptes (Boisduval), but some authors, e.g., Pratt and Emmel (1995), treat these subspecies as species and further subdivide them into subspecies. We follow their treatment.

© 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.