Royal Alberta Museum: Invertebrate Zoology - Bug Facts

[Caterpillars and Other Immature Insects]

Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Canadian Tiger Swallowtail (Papilio canadensis)

Canadian Tiger Swallowtail mud puddling for mineral salts
Credit: Terry Thormin

Canadian Tiger Swallowtail, caterpillar just prior to pupating
Credit: Terry Thormin

INTRODUCTION

This is one of the most commonly noticed butterflies in Alberta, at least by people who get out into the country in the month of June. Caterpillars, on the other hand, are rarely seen, because most of their lives they are well camouflaged.

IDENTIFICATION

Throughout most of the province this is the only swallowtail butterfly that is predominantly yellow with black stripes on the front wings. It is also one of the largest butterflies in Alberta, with wingspreads up to 10 cm. The caterpillar of this species changes dramatically as it goes through its various molts. In the first two instars (those periods between molts) it looks just like a bird dropping. It then changes to be predominantly green with two large eyespots near the front end. Just before pupating, the larva turns dark reddish brown.

DISTRIBUTION

The Canadian Tiger Swallowtail is found throughout Alberta wherever there are good aspen or mixed forests. In North America it is found throughout most of Canada south of the Arctic Circle, with records extending north of the Arctic Circle to the coast of the Arctic Ocean in the Yukon, and south into the northern United States.

TIME OF YEAR

Adults are found from about mid-May through to mid-August, although June is the month when they are most numerous. Caterpillars can be found by about mid-July and may last until early September.

HABITAT AND HABITS

This is a butterfly of open mixed and deciduous forests, and forest edges, although it will wander into older city residential areas if they are well treed. Adults will nectar at a wide variety of flowers and also visit damp soil to get the mineral salts dissolved in the water. The latter behaviour is known as mud puddling. Caterpillars feed on the leaves of Trembling Aspen, various willows and domestic Crab Apple. Because of their superb camouflage and because they feed at night, the caterpillars are seldom seen.

SIMILAR SPECIES

Throughout most of Alberta, other species of swallowtails have more extensive black areas and lack the pronounced black stripes of this species. In southern Alberta, right near the Montana border, it is possible to find the rare Two-tailed Swallowtail, Papilio multicaudata. This is a larger species, usually with a wingspan of over 10 cm. It also has two tails on each wing, one long one and one shorter one, whereas the Canadian Tiger Swallowtail only has one.

COMMENTS

Most of the requests we receive are for information on the caterpillar, rather than the adult butterfly. Most people are just curious to find out what the caterpillar is, although occasionally people are concerned that it might be damaging their trees and shrubs. This species is never found in sufficient numbers to do serious damage to its host plant.

For information on how to over-winter pupae of this species, see How to over-winter butterfly and moth pupae

For more information on the Canadian Tiger Swallowtail you can visit the University of Alberta’s entomology collection species page.

[Royal Alberta Museum Home Page] [Invertebrate Zoology]

For more information on this bug, please contact the Bug Room.
© Copyright 2000-2008, Royal Alberta Museum - ALL RIGHTS RESERVED
Last update: December 10 2004