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Tiger swallowtail caterpillars

Jeffrey Hahn, Extension Entomologist

People have been finding tiger swallowtail caterpillars in the landscape recently. They have been on the move as they look for places to pupate. Upon first sight, this insect is quite mysterious looking. It is up to a little over two inches in length. The body is either brownish or greenish with a yellow stripe circling the body somewhat near the head.

What stands out, however, are two large yellow and blue eyespots in front of the yellow stripe. This gives the
Tiger swallowtail caterpillar. Note the
orange osmeterium near the head and
the yellow and blue eyespots.  Photo:
Howard Ensign Evans, CSU State Univ.
caterpillar a rather menacing appearance. To further enhance this threatening look, the caterpillar can swing its head from side to side, mimicking a snake. And if that was not enough to keep someone at bay, it can evert a forked structure called an osmeterium near the head. This structure can not only startle someone but can also emit a foul odor to help protect the caterpillar.

Despite all of its bluster, a tiger swallowtail caterpillar is perfectly harmless to people. Don’t be alarmed if you see one, just let it go on its way and know it will grow to be a beautiful tiger swallowtail butterfly.

To see more pictures, see the eastern tiger swallowtail entry in BugGuide
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