Pale Swallowtail

Pale Swallowtail

Pale Swallowtail

April flowers bring May flowers. . . . I planned to highlight a wildflower in the first post of May. However, while hiking along Lower Hat Creek (Shasta County CA) Leonard found this cooperative pale swallowtail (Papilio eurymedon) for me to photograph. In a way butterflies are “flowers” of the insect world.

Pale swallowtails are common in dry montane forests, open woodlands and forest clearings from the Rocky Mountains to the Pacific Coast and from British Columbia to Mexico, although Nevada and Western Utah do not have large populations. The adults are diurnal and fly from late spring through late summer.

Pale swallowtail forewings are white with broad black discal bars and a black border. Their hindwings are also white and have a black median stripe, white marginal spots, blue and orange postmedian spots, a scalloped wavy margin and a long tail on each hindwind. Pale swallowtails have a black abdomen, a black thoraxwith two white stripes and their heads are black.

Adult pale swallowtails feed on nectar while their caterpillars feed on the leaves of hardwoods and other shrubs, particularly those of the Ceanothus genus.

The adult female lays spherical eggs singly on its caterpillar’s food plants. There is only one brood a season. The caterpillar spins silken mats on leaves then curls up in the leaves for shelter. Pale swallowtails overwinter in a chrysalis that is brown and resembles a free-hanging piece of bark.

The pale swallowtail looks similar to western tiger and two-tailed swallowtails. (see the post “Two-tailed Swallowtail” 07-04-2012P. eurymedon is white where the other two swallowtail species are yellow – “pale” in comparison.

Pale tiger swallowtail and pallid swallowtail are also common names for this large butterfly.

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