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This species is similar to subspecies of the Old World Swallowtail (P. machaon). The Anise Swallowtail occurs together with P. machaon throughout most of Alberta, and the following characters will distinguish these two species in most cases: the black pupil of the hindwing eyespot is centered and unconnected in P. zelicaon, while in P. machaon it is connected to the wing margin or positioned below the red scales. Differences in the mitchondrial DNA also distinguish these species (Sperling & Harrison 1994). Hybrid individuals displaying characters intermediate between P. machaon and P. zelicaon are occasionally found where the range of these species overlap, and can be common in some regions, such as the central Alberta foothills (Sperling 1987, Sperling 1990). To add to the challenge in identifying members of this confusing group, a black colour form of P. zelicaon, P. m. dodi and zelicaon X machaon hybrids occurs, in which adults have most of the yellow colouration replaced by black (Sperling 1987). The black form of P. zelicaon was once thought to be a separate species, P. nitra.

The immature stages are very similar to the Old World Swallowtail. Eggs are pale yellow and round, with visible reddish areas on the top and sides as the larva develops (Guppy & Shepard 2001). Eggs are laid on the flower heads and leaves of the hostplant (Bird et al. 1995). The first three larval instars resemble bird droppings, coloured black with a white saddle, and later instars are green with black bands and yellow to orange spots (Sperling 1987). The pupa has a projection on each side and a row of projections along the dorsum; it varies in colour from yellow-green to brown (Guppy & Shepard 2001). Adults commonly nectar at Common Dandelion (Taraxacum officinale), and males fly to hilltops to await females (Bird et al. 1995).

Larvae feed on various umbellifers (Umbelliferae) in Alberta, depending on habitat and geographic location. Confirmed hosts include Cow Parsnip (Heracleum lanatum), several species of Angelica (Angelica arguta, A. dawsoni, A. genuflexa), wild parsleys (Lomatium dissectum, L. triternatum), Water Parsnip (Sium suave), and Heart-leaved Alexanders (Zizia aptera) (Sperling 1987).