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The Swallowtails’ Tale

Apr 18, 2016

In nature no insect is quite like the swallowtail.

Swallowtail butterflies have extensions on their hind wings that resemble the tail of a swallow. This feature makes swallowtails an easy group of butterflies to recognize.

Swallowtails are big butterflies with wingspans from two to nearly six inches. Some of these butterflies are easy to identify, too. The swallowtails with bold black-and-white stripes are tiger swallowtails. And the black swallowtails… are black swallowtails.

Swallowtail caterpillars are distinct from one another, and their appearance helps protect them from predators. Giant swallowtail caterpillars are dark with irregular white markings. They resemble bird droppings–a mimicry that puts off would-be predators. The tiger swallowtail and spicebush swallowtail caterpillars have large eyespots toward the rear of their bodies. These eyespots divert predators from the insect’s head. A spicebush swallowtail larva will also curl a leaf, wrap up in it, secure it with a strand of silk, and hide in its makeshift shelter.

All true swallowtail caterpillars have a unique defense: Each has a Y-shaped gland on its body that can emit a foul odor when the insect is disturbed.

Spotlight on the Spicebush Swallowtail

The spicebush swallowtail is a  blackish swallowtail with iridescent blue (females) or green (males) on the hindwings
  • The larvae of the spicebush are bright green, smooth, with a prominent pair of black and yellow eyespots on a hump behind the actual head, and two more yellow spots behind those.
  • There are 3 broods, with adults flying from April into October. Larvae hide in shelters made by spinning silk onto the surface of a leaf of the food plant, causing the leaf to curl around them.
    Larvae eat sassafras and spicebush, making a folded-over “tent” out of a leaf of the food plant to conceal itself when not feeding. Adults drink nectar from many flowers, but especially from butterfly weed.
  • The spicebush swallowtail is a common breeding resident in the State of Missouri.

Discover more about all swallowtail species with the MDC’s Field Guide.

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