Battus philenor hirsuta, the California pipevine swallowtail or hairy pipevine swallowtail, is a subspecies of the pipevine swallowtail that is endemic to Northern California in the United States. The butterfly is black with hindwings that have iridescent green-blue coloring above and a row of red spots below; the caterpillars are black with fleshy protrusions and orange spots. This subspecies is smaller in size, hairier, and lays eggs in larger clutch sizes than the nominate subspecies. The egg clutches are deposited on the shoot tips of the California pipevine, a perennial vine native to riparian, chaparral, and woodland ecosystems of the California Coast Ranges, Sacramento Valley, and Sierra Nevada foothills. The larvae feed exclusively on the foliage and shoot tips of the pipevine, although adults eat floral nectar from a variety of plants. The plant contains a toxic substance, aristolochic acid. The larvae sequester the toxin, and both the juvenile and adult butterflies have high and toxic concentrations of the aristolochic acid in their tissues. Throughout the range of the species, Battus philenor, other butterflies and moths mimic the distinctive coloration of the swallowtail to avoid predators. However, there are no known mimics of the Californian subspecies.

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