Recorded at all sites. The Western Tiger Swallowtail is basically a species of riparian forest, where it glides majestically back and forth along the watercourse. It has expanded into older urban neighborhoods where several of its host genera are grown as shade trees, and behaves as if the street were a watercourse. In the high country and on the Sierran east slope its usual host is Aspen.
One brood (June-July) at higher elevations; one and a partial second at Washington; 2-3 at lower elevations with a long flight season (late February or March-September or October). An avid puddler. Visits Yerba Santa, California Buckeye, Milkweed, Dogbane, Lilies, Coyotemint, etc., etc. and in gardens frequent at Lilac and Buddleia. Spring individuals are smaller and usually paler than summer. Low-elevation hosts include Sycamore (Platanus), Ash (Fraxinus), Cherry and other stone fruits (Prunus), Willow (Salix), Privet (Ligustrum), Lilac (Syringa) and (in Sacramento County) Sweet Gum (Liquidambar).