Canadian Tiger Swallowtail
Diagnosis: The Canadian Tiger Swallowtail is one of the best-known butterflies in this country because of its size (wingspan: 53 to 90 mm) and distinctive pattern. The yellow ground colour with wide, black tiger stripes catches the attention of even the most casual observer. It has a wide, black band along the inner margin of the hindwing. The underside is yellow, often with extensive over-scaling of orange, and black.
Subspecies: None (but see Western Tiger Swallowtail). Since 1906, when it was first named, canadensis has been considered a subspecies of the more southerly Eastern Tiger Swallowtail (P. glaucus), found throughout the eastern U.S. It was separated by Hagen et al. (1991), and others, based on detailed physiological and genetic characteristics. The more northern butterfly has only one generation per year, while glaucus has two. Another distinctive difference is that the Canadian Tiger Swallowtail does not have the black female form that occurs in glaucus. Oddly enough, the only exceptions to this rule are the occasional all-black females that have appeared in Newfoundland, despite the fact that they do not appear in New England (Morris, 1980).
Range: This butterfly is found in all provinces and territories. Its range extends north of the Arctic Circle in Yukon, and to Churchill in Manitoba, Little Shagamu River in Ontario, and to Schefferville in Quebec. It has not been reported from Labrador.
Similar Species: The Eastern Tiger Swallowtail (P. glaucus) is best recognized by geographic location and the width of the black stripe along the anal margin, which is considerably narrower in glaucus. The Western Tiger Swallowtail (P. rutulus), the Pale Swallowtail (P. eurymedon), and the Two-tailed Swallowtail (P. multicaudatus) differ as described under those species. [compare images]
Early Stages: The mature larvae are dark green, with two spots that look like eyes on the swollen section of the body behind the head; this creates a snake-like profile. Immature larvae are brown and white, resembling bird droppings. The larvae use a wide variety of trees as foodplants, including willow (Salix spp.), cherry (Prunus spp.), poplar (Populus spp.), and ash (Fraxinus spp.).
Abundance: The Canadian Tiger Swallowtail is common to abundant through most of its range.
Flight Season: This species has only one generation per year, usually appearing in mid-May and flying to late July depending on latitude.
Habits: This is mainly a species of open woodlands and adjacent areas, but it also flies north of treeline in Canada where stunted trees and dwarf willows can be found. It can even be seen on the wing in city backyard gardens. The Canadian Tiger Swallowtail is an avid mud-puddler and sometimes hundreds will gather at the same small puddle, jostling for position.
Remarks: Although a relatively large butterfly, particularly in southern Canada, extremely small examples can be found. PWH captured a small male with a 50 mm wing expanse in the Cypress Hills of Saskatchewan that appeared not much bigger than a large sulphur. A number of striking semi-melanic specimens have been taken, including one near Ottawa by RAL in 1976 that was mostly black.
© 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.
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Date Modified: 2010-05-31