2 5/8-3" (67-76 mm). Yellow-banded; more yellow than black. Lemon-yellow spots in midwing band above are straight-edged and fill spaces between veins of wing; HW flushed with blue between broad, yellow band and medium-long tail; HW eyespot orange with large, round, centered pupil. Similar below. Black abdomen has yellow side stripes.
Desert Swallowtail has outwardly convex, yellow spots on wings. Oregon Swallowtail is darker yellow, has yellow abdomen with black lines, and concave spots that are scalloped inward, away from margin. Yellow ("brucei") form of Western Black Swallowtail has off-center pupils, and yellow abdomen with black stripes.
Immature stages variable. Generally, yellow eggs hatch green, black-banded and orange-spotted caterpillar, to 2" (51 mm), which forms green or brown twiglike chrysalis, to 1 1/4" (32 mm). Both young leaves and flowers or buds of many species are consumed, including fennel (Foeniculum vulgare), seaside angelica (Angelica lucida), and cow parsnip (Heracleum lanatum), as well as carrots and parsley (Apiaceae), and citrus trees (Rutaceae).
Varies greatly: year-round in S. California; distinct spring and fall broods on Northwest Coast, 1 brood midsummer at high altitudes in Rockies.
Everywhere from sea-level tidelines to 14,000' (4,270 m) mountaintops, vacant city lots to sage deserts, canyons, and parks. Absent from dense forests except clearings or roadsides.
Pacific Coast from British Columbia to Baja California, east to Black Hills and eastern edge of Rockies; scarce or absent in most of SE. California deserts.
The Anise Swallowtail is one of the most adaptable native butterflies, along with the Eastern Black Swallowtail. Males are especially ardent hilltop fliers, and seek out any eminence on the horizon as a courtship rendezvous