Ugly Duckling Orangedog Caterpillars

By University of Arkansas

09-14-2009

Disguised as bird droppings, the orangedog caterpillar is the classic case of the ugly duckling that eventually turns into a swan.

These caterpillars are native to Arkansas and range from Michigan in the north to western Connecticut in the east, all the way to Florida and Texas. They have a remarkable appetite for cultivated citrus.

Daniel Beasley, Jefferson County extension agent for the University of Arkansas Division of Agriculture, and county extension Staff Chair Don Plunkett spotted orangedogs of various sizes and ages in a homeowner’s lemon tree.

A second homeowner with the same infestation in her citrus told Plunkett that she had taken to using the “smooshing them” method of pest control.

“They look like bird droppings on the lemon tree leaves,” said Don Plunkett, Jefferson County extension staff chair for the U of A Division of Agriculture. “The larger ones actually took on a tree bark look and those could in some cases blend onto the tree trunk.”

Plunkett said it was larvae that “neither of us had ever seen before.” The two shot photos and video of the caterpillars.

Gentle prodding by the agents agitated caterpillar.

“What came next was a shock,” Plunkett said. “The creatures began to stick out what appeared to be a red, forked tongue and this pretty well scared these two county Extension agents into not wanting to handle the larvae!”

The sight was immediately followed by a foul odor.

The two consulted with John Hopkins, extension urban entomologist for the division of agriculture, to solve the mystery of the bizarre-looking creature.

“The caterpillar is the larval form of the Giant Swallowtail butterfly,” Hopkins said. “They’re usually seen from July to October, and produce at least two generations a year in Arkansas.”

The forked tongue Beasley and Plunkett saw was a scent gland, which all swallowtail larvae possess. The caterpillar emits the odor as a defense when disturbed.

“The orangedogs feed on cultivated citrus, hoptree, prickly ash, torchwood, wild lime and other plants in the citrus family,” Hopkins said.

The odd name - orangedog - refers to their habit of showing up in orange and other trees.

Once the second homeowner learned what the orangedog caterpillar would become, she quit the smooshing.