Subject: Leaf-eating mutant?
Location: Knox County, near Oak Ridge, TN
August 28, 2012 9:53 pm
A colleague and friend has watched this creature destroy a small tree for the last few days. Her home is in north Knox County in East Tennessee, near the Oak Ridge National Laboratory (ORNL). I’ve exhausted my attempts to identify this tiny monster. Please help?
Signature: EconProfLikesBugs

Caterpillar of Viceroy or Admiral???

Dear EconProfLikesBugs,
This caterpillar will metamorphose into a beautiful butterfly in the genus Limenitis, but we are uncertain of the species.  According to BugGuide:  “Caterpillars and pupae are very distinctive, and not easily confused with anything else in North America. They are roughened by many small tubercles and a few pairs of large bumps and “horns”; they also have a more obvious pair of long studded horns, almost looking like “antlers” just back of the head. They tend to hold their bodies so as to look hunch-backed at the thorax, and they are colored to resemble bird droppings in shades of dark dull brown or green with white to cream colored patches. Some Swallowtail Caterpillars are similar in shape and coloring, but don’t have the studded appendages of Limenitis caterpillars.  Telling the caterpillars of the various species of Limenitis from one another is very difficult. Typically only two (occasionally three) species are found in any given area, and this helps, especially since one is usually the Viceroy. Viceroy caterpillars tend to be found, almost always, on Willows or Cottonwoods near water. They average more spiny at each stage of development (except the first instar, which isn’t very spiny in any of the species). They also have the pair of humps near the front of the abdomen smaller with more noticeable spines on top. Generally the long pair of spines behind the head is relatively light in color in Viceroy caterpillars, but more often much darker in other species. There are often color differences between species, but they vary from region to region. So, for instance, Viceroy caterpillars in the West have much less white coloring than other species, but in the Southeast they actually tend to have more. The remaining species and subspecies of Limenitis have caterpillars that are extremely similar, and there may be no reliable way to tell them apart. Luckily, they mostly occur in separate regions.”  Our best guesses are that it might become a Viceroy, the mimic of the Monarch, or it might metamorphose into a Red Spotted Purple, which we consider to be the most beautiful butterfly in North America.

Possibly Red Spotted Purple Caterpillar

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