Common from the lower foothills to tree-line; not often seen in the Central Valley. Our only tiger-striped Swallowtail with a white or whitish ground color, and the only one that is always single-brooded (April-August at low elevations, June-September in the high country). Males patrol canyon bottoms but also hilltop, especially in chaparral. Both sexes are avid flower visitors. In the foothills they are often seen on Vetch, Yerba Santa, Blue Dicks, Ithuriel's Spear, and California Buckeye.

This small, black-and-yellowish-white swallowtail occurs on rocky, treeless balds - on serpentine at low elevations and at and above tree-line. On our transect it occurs sporadically at Donner Pass but consistently at Castle and Basin Peaks. Males puddle. They patrol parallel to ridgetops but just below them, unlike the Anise Swallowtail which dominates the actual summits. A usually uncommon species with tremendous geographic variation over its range, but no significant variation in our area.

Generally uncommon in our area, largely confined to riparian corridors where it is greatly outnumbered by the Western Tiger Swallowtail. Generally rare to absent on the floor of the Central Valley. (Why?) Adults soar high in the trees, the males patrolling stream courses and roads. Two or three broods in the foothills; perhaps only one at Sierraville and at Verdi, NV, where quite common. Visits California Buckeye, Yerba Santa, Giant Hyssop, Milkweed, Lilies, and other large, showy flowers.

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.

The Anise Swallowtail is a complex set of ecological races, or "ecotypes," whose seasonality has been adjusted by natural selection to match that of their host plants. Selection for adaptive life-history traits seems to have proceeded much faster than evolution at the level of neutral molecular loci.