Bug of the Week

Black and Tiger Swallowtails (Papilio polyxenes and Papilio glaucus)

Greetings, BugFans,

The Eastern Black swallowtail is one of the earlier-seen of the butterflies that do not actually overwinter as an adults (Mourning Cloak, Angle-wings; featured in an earlier B-o-t-W). Black swallowtail males (which, like many butterfly species are smaller than the females) often appear in late April and early May. The female is larger, lacks the yellow on the wings and has a blue wash above the tails.

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Black swallowtail male extends its proboscis to find minerals on a gravel road. Pipevine swallowtails are very uncommon in Wisconsin.

Another name for the Black Swallowtail is the Parsley Swallowtail, because the larval food plants are mainly in the carrot/parsley family (Apiaceae). Black swallowtails have benefited from the increase of gardens and agriculture and is declining in spots where agriculture is on the wane and forests are returning. The adults really like nectaring on clovers.

Like zebras, Black swallowtail caterpillars use a disruptive pattern; in the broken sunlight, it’s hard for predators to discern their true shape. In a pinch (or – when pinched…), it can emit a noxious odor. Pupae that overwinter emerge in May; the second brood of the summer spends only 9 days in the pupal case.

Some stripes may still be seen on the dark morph of the Tiger swallowtail.

Females of the Eastern Tiger Swallowtail may be yellow and black, or they may be black. The Black morph occurs more frequently in the southern part of their range; where they are mimicking the Pipevine Swallowtail, which is poisonous/noxious because its caterpillars feed on the poisonous Pipevine plant. Black Swallowtails have yellow spots on the body; tigers have a yellow streak along each side of the thorax and abdomen in both morphs.

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Black swallowtail caterpillar on Queen Anne’s Lace stem. Tiger Swallowtails are among the largest butterflies around, reaching 5” in wingspan.

The Tiger’s larval food plants are trees of woodland openings like poplar, basswood, cherry and ash. Tiger swallowtail caterpillars have two big eyespots toward their rear, all the better to scare predators with, my dear.

Sunny days,
The BugLady