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Faded specimens of P. canadensis or P. rutulus can be similar to the Pale Swallowtail, but the black stripes of P. eurymedon are much broader, and the ground colour is white or creamy white, never yellow. No subspecies are currently recognized.

The egg is yellowish green, round and smooth, developing a pink tinge along the sides several days after being laid (Guppy & Shepard 2001). Larvae are similar to those of other species in the tiger swallowtail group (Layberry et al. 1998); young larvae are black with a white saddle, resembling bird droppings, while mature larvae are bright green with a whitish underside, and have a pair of yellow and black eyespots on the mid-thoracic segment (Guppy & Shepard 2001). The pupae are green or brown, with darker longitudinal lines (Guppy & Shepard 2001). Adult males patrol forest edges and watercourses in search of females, and (unlike the other tiger swallowtails) also congregate at hilltops to await females (Layberry et al. 1998). Males form mud-puddling congregations (Layberry et al. 1998).

The larval food plant is unknown in Alberta. It is most likely one or more shrub species in the rose (Rosaceae), birch (Betulaceae) or buckthorn (Rhamnaceae) family. In BC, larvae feed on cultivated apple (Malus spp.), Red Alder (Alnus rubra), birch (Betula spp.), tea bush (Ceanothus sanguineus), Ocean Spray (Holodiscus discolor), and Cherry (Prunus emerginata) (Guppy & Shepard 2001).