Orange Dog, Vol. 10, No. 10
Orange Dog
Papilio cresphontes
Order: Lepidoptera
Family: Papilionidae
Strange name for a caterpillar. They are not orange, and they are not dogs. They do eat orange tree leaves.
Orange dogs grow up to be the largest butterflies in the country, giant swallowtail butterflies. Large specimens have wing spans of over six inches, though four to five inches is more common. The caterpillars are big too, ranging from two to three inches when fully grown.
Giant swallowtail butterflies are easy to identify because of their size and unique wing pattern. The upper wings are mostly black or dark colored with a large yellow band across both forewings. When butterflies are in flight, or resting with their wings expanded, this band extends straight across the center of both wings. There is also a smaller yellow band near the margin of each hind wing.
Quite a few caterpillars mimic bird poop when young, but orange dogs never outgrow this look. Sometimes it pays to be ugly and unappealing. This is an effective strategy for avoiding predators, but orange dogs, along with caterpillars of other swallowtail butterflies, also have a more active defensive trick.
If disturbed by a potential predator, orange dogs suddenly sprout large, colorful “horns,” and assume a threatening, “in your face” posture. To a foraging blue jay this may feel like a face-to-face encounter with a snake extending its forked tongue. This snake head mimicry is even more pronounced in some other species of swallowtails that have enlarged thoracic areas with large eyespots. These defensive structures, called osmeteria, are usually stored inside the body, just behind the head. Think of a pair of elongate balloons that can be inflated and deflated at will. The osmeteria in the photo are only partly extended and were about twice this length when fully everted. Everting the osmeteria also releases a strong, unpleasant odor, which further discourages would-be predators.
Because citrus is a key host, one might think giant swallowtails are restricted to southern regions of the country. But giant swallowtails occur throughout most of the eastern US because they also feed on other members of the Rutaceae family, such as prickly ash, hop tree and Hercules club. Hercules club, aka toothache tree, is one of the more interesting host trees found in the Southeast. The trunks are covered with large, stout, somewhat pyramid-shaped spines. There are also pairs of sharp spines along the center vein of the compound leaves.
Control: It is not often one needs to control caterpillars of a butterfly, especially such a large and beautiful butterfly. But it does not take many big orange dogs to defoliate a small orange or lemon tree, and owners of such trees usually want to avoid such damage. Insecticides containing spinosad (FertiLome, Monterey, Bonide, etc.) or zeta-cypermethrin (GardenTech) work well against small caterpillars. But if you want preventive control, and not just revenge, it is important to monitor plants closely and treat while caterpillars are small. Big caterpillars are more difficult to control and will have already eaten a lot of leaf area.
Parsleyworm, the caterpillar of the black swallowtail butterfly, is another swallowtail butterfly that is sometimes considered to be pest and sometimes encouraged and appreciated in butterfly gardens.
Thanks to Sally and Wayne Stroupe and Linda Baudo for providing this caterpillar to photograph. It pupated successfully, spent the winter on my desk as a chrysalis, emerged as a butterfly this April, and was photographed and released.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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