Caterpillar Extravaganza

This past weekend I attended the third annual "Caterwauling for Caterpillars" night. Despite the strange name, this event is a yearly gathering of insect-loving Ohio University students who have one goal in mind: find cool caterpillars. Although the overall diversity wasn't too great this year, we still saw some interesting "cats," and I wanted to highlight a few of them here.

First up is the Saddled Prominent (Heterocampa guttivitta). This wide-ranging species is quite variable in appearance, and it took me awhile to figure out just what species of prominent (Family Notodontidae) this individual was. The main identifying features are the saddle on the top of the 3rd and 4th abdominal segments (the two segments which have the first and second prolegs), the white line running down the body near the back (subdorsal line), and the brown and white band on the head. The Saddled Prominent is a generalist when it comes to host plant preference. Unlike some caterpillar species which feed on only one or a few species of plants, the caterpillar of the Saddled Prominent feeds on pretty much any woody plants, including American Beech, birches, buckeyes, dogwood, hickories, maples, oaks, sumacs, and many other trees and shrubs.

A relatively common species in southeast Ohio—yet one that I always enjoy seeing—is the Giant Leopard Moth (Hypercompe scribonia). Although you can't really tell from the photo, Giant Leopard Moth caterpillars are large. They're also extremely easy to identify; if you see a large black caterpillar covered in black bristles, with red rings where each abdominal segment meets, you've got yourself a Giant Leopard Moth. The caterpillars of this species feed only at night, spending most of the daylight hours hiding out on the forest floor. Although the black bristles (which are technically called "setae") look formidable, the Giant Leopard Moth does not actually sting. Instead, they will simply roll up into a ball if threatened and hope that they look scary enough for the threat to leave them alone. If you want to read about the adult Giant Leopard Moth, check out my previous post "Mothing at Clear Creek: The Showy."

A few minutes after seeing the Giant Leopard Moth caterpillar, another strikingly-similar caterpillar crossed our paths. This is the caterpillar of the Agreeable Tiger Moth (Spilosoma congrua). Like many other species of insects, the Agreeable Tiger Moth is able to sequester toxins found in the plants that they eat in order to become toxic themselves. In the case of this species, these caterpillars sequester iridoid glycosides. Although the levels of iridoid glycosides aren't very dangerous to most potential predators of the Agreeable Tiger Moth, they do make the caterpillar taste pretty nasty, which would hopefully deter any predators from eating this species. Caterpillars of the Agreeable Tiger Moth come in two color morphs: one with colored rings, and one with red dots down the side of the body. Although I couldn't find any information about the two morphs, it would be interesting to see if there are any differences between the two—whether they occur in different geographic locations, or if they have differences in the iridoid glycoside sequestration, or the likes. 

By far the most abundant type of caterpillar of the night were the geometers. Geometers—better known as "inch worms"—are moths belonging to the family Geometridae. The geometer family is huge, with over 1,400 species in North America (and several hundred in Ohio alone). Identifying geometer caterpillars can be incredibly difficult, especially since many of them are incredibly camouflaged and lack much in the way of obvious identifying characteristics. Although I couldn't identify the one pictured above to species, it was my favorite geometer of the night. This caterpillar is a perfect twig mimic. I would have never seen him had I not had a UV flashlight. UV flashlights are indispensable tools when searching for caterpillars. Most "caterpillaring" occurs under the cover of night, when caterpillars are most active. It just so happens that most caterpillar species fluoresce when exposed to ultraviolet (UV) light. If you walk around the forest with a hand-held UV flashlight—which you can easily find on Amazon—the caterpillars will quite literally light up, making it much easier to find cryptic species. 

One of the most peculiar species of the night was the Black-Waved Flannel Moth (Lagoa crispata). The caterpillar of the Black-Waved Flannel Moth is rather ridiculous looking in my opinion, appearing like a frizzy toupée. But don't let its appearance fool you—flannel moth caterpillars are not one to mess with. This caterpillar has two lines of defense. First, all those long hairs you see are urticating setae, which are essentially bristles which can break off into your skin causing irritation (like dozens and dozens of tiny splinters). But hidden within the urticating setae is the second line of defense: short, venomous spines. Being stung by the caterpillar of any flannel moth species is not a pleasant experience, but the Black-Waved Flannel Moth is one of the least painful of the bunch (the Southern Flannel Moth, Megalopyge opercularis, wins the pain contest).

I couldn't talk about the Black-Waved Flannel Moth without at least showing what an adult looks like. The adult Black-Waved Flannel Moth is one of the most fuzzy moths out there. Unlike the caterpillars, the adults are completely harmless. This individual was found in Ross County earlier in the summer.

The last three species I want to highlight are all slug caterpillars from the family Limacodidae. The "slugs" are almost always a favorite of anyone into Lepidopterans (moths and butterflies). Slug caterpillars are called such due to their rounded, slug-like appearance. They hug whatever surface they are clinging too, and move around in a manner more like a slug than a caterpillar. Some slugs—like this Jeweled Tailed Slug (Packardia geminata)—can be rather dull in appearance. Others can be stunningly beautiful.

Many slugs are tiny (quarter sized or less) and mostly green. However, many species are adorned with stinging hairs, such as this is Nason's Slug (Natada nasoni). The spines of the Nason's Slug are unique compared to many other slug caterpillars. These spines are actually retractable, and most of the time the caterpillar will only have the tips of the spines exposed. If the caterpillar feels threatened, it will extend its spines and hopefully scare the threat away. If not, the threat (whether it be a bird, human, or whatever) will receive a painful sting. This was a good species to find for the night, as the Nason's Slug is restricted to only the southern and southeastern portions of the state.

The highlight of the night—at least in my opinion—was this Saddleback caterpillar (Acharia stimulea). The Saddleback is one of the most well-known slug caterpillars, and it's easy to see why. Even someone who doesn't care about insects would be hard-pressed to ignore one of these cats. As you can tell from the photo above, the common name for this species is due to the circular "saddle" on its back. But if any feature is grabbing your attention, it's most surely all the protruding appendages covered in spines. These spines pack quite a punch. Each spine is rigid, incredibly sharp, and most importantly hollow. At the base of each spine is a venom gland. If a spine comes in contact with exposed skin, it breaks off into the skin and begins releasing venom. The Saddleback's venom is both vesicating and hemolytic, meaning that it causes your skin to blister while also breaking down your red blood cells and damaging your tissue. A sting from one of these caterpillars will cause immediate localized pain (fellow blogger Andrew Gibson likened it to "burning knives"), and in extreme cases can also cause nausea, migraines, and a host of other symptoms. The effects of the venom can last upwards of 5 hours. 

On the front end of the Saddleback are two large white spots. These are thought to mimicking eyes. Fake eyes are common in insects—especially in Lepidopterans—and these eye-spots serve to scare away potential predators by either startling the predators or conveying that the animal in question is dangerous.

Like always, this year's Caterwauling for Caterpillars event was fantastic. If you want to read about some of the caterpillars from the first Caterwauling for Caterpillars night, please check out my post entitled "Caterpillars, Caterpillars, and More Caterpillars." And if you are interested in seeing some caterpillars yourself, mid-September is the best time for that in Ohio! Get out and see what you can find!