Summer brings swallowtails

By Claire Curry | Published Thursday, July 29, 2010

The hot weather of summer makes it miserable outside for us humans sometimes, but it is a great time of year to look for butterflies. Right now we have quite a few large showy swallowtails out and about.

We have four species of swallowtails: Pipevine, Black, Giant and Eastern Tiger. As a group, they are very distinctive with bold black, yellow and iridescent blue patterns and the “tails” on the wings for which they are named. However, the species can be hard to tell apart sometimes.

The Giant Swallowtail has the most distinctive pattern. It is black with yellow stripes on the upper surface of the wings. One band of yellow goes from wingtip to wingtip on the front wings. The second band of yellow goes along the trailing edge of the wing from the front wings to the hind wing. Below, it has more yellow and some orange and iridescent blue highlights. The caterpillars feed on trees in the citrus family, such as prickly ash. They are brown with white blotches, making them look rather like bird poop.

Eastern Tiger Swallowtails are also large with a black and yellow pattern, but they have more yellow above. The black on their wings consists of a broad black edge and black tiger stripes. There is some iridescent blue both above and below on the hind wings and a few orange spots below on the hind wings. This species also has a dark form of the females.

The dark female tiger swallowtails have two rows of orange spots below; sometimes you can also see the faint tiger pattern under the dark color. This dark form mimics the noxious-tasting Pipevine Swallowtail. Tiger swallowtail caterpillars (mostly green with a fake black-and-yellow “eye” near the head) eat leaves from various woody plants such as cottonwoods, cherry and magnolia trees, while the Pipevine Swallowtail caterpillars eat the toxic pipevines. Pipevines contain aristolochic acid, which is retained in the adults, making them unpalatable to predators.

Pipevine Swallowtails are black above with iridescent blue hind wings and one row of white spots along the wing edges. Below, the hindwings have more blue and one row of orange spots. Pipevine Swallowtail caterpillars are unique with fleshy protrusions of reddish-orange and longer black protrusions all over a dull black body.

The adult Black Swallowtail is another Pipevine mimic. Adults are mostly black with some blue iridescence on the hind wings, but can be distinguished by two bands of yellow around the wing edges above and two bands of orange spots below on the hindwing. The caterpillars of this species feed on members of the carrot family (Apiaceae), such as parsley, dill, fennel, carrots and Queen Anne’s lace. I’ve found lots of caterpillars on the wild prairie parsley that blooms in spring and early summer. Their color scheme is green with black bands; each black band has yellow-orange spots in it.

Adult swallowtails feed on flowers and can also be seen “puddling” at mud or moist ground (they are likely seeking minerals). I refer to the “Kaufman Field Guide to Butterflies of North America” by Jim P. Brock and Kenn Kaufman and “Caterpillars of Eastern North America” by David L. Wagner when I have trouble identifying the adults and caterpillars, respectively. If you venture outside in this hot weather, keep your eyes peeled. You never know what beautiful butterflies you might find!

The next monthly field trips on the Lyndon B. Johnson National Grasslands are Aug. 4 and Sept. 1. We will depart at 9 a.m. from the Forest Service District Office in Decatur. For information, contact Mary Curry (see below) or the Forest Service, (940) 627-5475.

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