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!

Fact Check: "Poisonous Canadian Caterpillar Invades Midwest!"

Every year around the beginning of Autumn I see a story passed around on various social media outlets, especially Facebook. All these stories are titled something to the effect of "Poisonous/Venomous Caterpillar Found in *assorted locations*," and they're all about the little caterpillar of the Hickory Tussock Moth. Even news outlets pick this story up. Sadly, the claims these stories make are pretty much completely wrong. Here's a fact check on the Hickory Tussock Moth.

The Hickory Tussock Moth, Lophocampa caryae, is a species belonging to the Tiger Moths (Tribe Arctiini). The rather dashing adults look like this. The caterpillars, on the other hand, are black and white. These caterpillars are covered in white hairs with a central line of black hairs running down their back.

Reports of the Hickory Tussock Moth courtesy of Butterflies and Moths of North America.

The first thing I want to clarify about this species is their range. Most stories act like these caterpillars are rare in whatever state they're writing about, and that they are coming in from some other location. One of the most hilarious stories I've seen claimed this was a native Canadian species that was "invading Ohio." The Hickory Tussock Moth is actually a really common species throughout New England and the eastern Midwest. Their range also extends north to the very southern portion of the Canadian province of Ottawa. If anything, these aren't a "Canadian species," but an American one that barely extends into Canada. And these caterpillars aren't exactly rare across their range either. I've seen a dozen or so during a single hike before, and that was without trying to look for them. 

But the main thing I want to talk about is their supposed venom/poison, which many stories will say is very dangerous to humans. First, let's clarify what poisonous and venomous means. Poison means a toxin that is ingested (i.e. if you eat it and get sick, it's poisonous). Venom is a toxin that is injected into you via fangs, a stinger, or some other modified part of the body (i.e. if it bites or stings you and you get sick, it's venomous). Unless you plan on eating a caterpillar, the only way it could be dangerous to you is through venom. But is the Hickory Tussock Moth caterpillar venomous?

The short answer is no, the Hickory Tussock Moth caterpillar is not venomous; however, it is a bit more complicated than that. So, let’s start with the basics. Many caterpillar species are covered in hairs called setae. These setae help with sensation, like how a cat’s whiskers do. Many times these setae are harmless (like in the Woolly Bear), but in some species these hairs can break off into an animal’s skin and cause irritation, sort of like a cactus’s spines or bristles. In some other species, like the caterpillars of the Flannel Moths, these setae have been modified into hollow spines, and at the bottom of the spines are venom glands, sort of like a bee’s stinger. The caterpillars with these spines and venom glands can truly be called a venomous caterpillar, but does the Hickory Tussock Moth caterpillar have these? The answer is no. Hickory Tussock Moth caterpillars do not have stinging spines nor venom glands (Hartmann 2009, Kuspis et al. 2001). They do, however, have the irritating setae that I previously mentioned. But, are they really that irritating?

Citations:

Hartmann, T., 2009. Tiger moths and woolly bears. Behavior, ecology and evolution of the Arctiidae.

Kuspis, D.A., Rawlins, J.E. and Krenzelok, E.P., 2001. Human exposures to stinging caterpillar: Lophocampa caryae exposures. The American journal of emergency medicine, 19(5), pp.396-398. Link.

People will often comment on these stories with horror stories about how either they or someone they know touched one of the caterpillars and had a horrible reaction, with some even saying they had to go to the ER. This is not the norm, at all. Some people are, for whatever biological reason, hypo-sensitive to the setae of this species. They can experience pain and bad rashes, yet the average person will not experience this. Let me give you an analogy. Some people are allergic to peanut butter, but the vast majority of people aren’t. Would you say peanut butter is poisonous/dangerous to the average human? No, you wouldn’t. It is the same with the Hickory Tussock Moth caterpillar. A very small percentage of people will have a bad reaction to the setae of this species, but the average person will either have no reaction, or they might itch a bit. To prove a point for science, I pet this Hickory Tussock Moth caterpillar. And not just once — I pet him several times. And what happened? Pretty much nothing. I had a few itchy sensations, but nothing hurt and there was no rash or anything. So much for being a scary and dangerous caterpillar!

Is the Hickory Tussock Moth a species to fear? Not at all! These little guys are just another victim of social media getting animal facts incorrect. It's especially sad to see news organizations (like CBS which claimed this caterpillar wasn't native to the US and that is has venom glands) perpetuating these incorrect "facts." Thanks for reading!

Hickory Horned Devil

This post is several weeks later than what I said it would be, but better late than never! Back at the beginning of September, I went to a caterpillar party (because that is the kind of party wildlife biology majors have) in northern Athens County. I made a post earlier on some of the more showy caterpillars we found over the course of the night, which you can read here. However, I felt the star of the night deserved a post all his own, and so here we are!

Meet the Hickory Horned Devil, Citheronia regalis. This awe-inspiring creature is the larval stage of the Regal Moth (also known as the Royal Walnut Moth). I'd like to go on a quick tangent for a second. That's a lot of names for one species, isn't it? This highlights one of the several problems with common names. All species, once discovered and described, are given one specific scientific name. In this case it's Citheronia regalis. There is no other animal with that name. If someone says that name, everyone knows what species they're referring to. On the other hand, common names are not that straightforward. The caterpillars are mostly called Hickory Horned Devils, but you could also correctly call it a Regal Moth caterpillar. The adults aren't often called Hickory Horned Devils, but instead are called Regal Moths or Royal Walnut Moths, depending on which you prefer. With so many names, it's easy for people to get confused and not know exactly what you're talking about. Often times, common names vary across geographical regions and from person to person, which is why I always give a scientific name (the specific two-part Latin name) in my posts in addition to a given common name. 

Naming aside, this is a monstrously-large caterpillar, as you can tell by the photo above. In fact, this is the largest caterpillar species in North America. It is worth noting that the adult moth isn't the largest moth in North America though (a title belonging to the Cecropia Moth). Although it might look terrifying (especially to those who aren't that keen on insects), the Hickory Horned Devil is completely harmless. The large horn-like projections on its head, which are technically named "scoli" (singular: scolus), are modified tubercles. You might think that these scoli can sting, as certain caterpillars can do, but these are only for show and they can't really harm anything. The Hickory Horned Devil runs solely on the bet that its appearance will scare off any potential predators, which is quite effective for the most part.

As you might have imagined, this caterpillar caused quite the ruckus amongst the group. I was taking photos of another caterpillar when I was completely startled by excited screaming coming from behind me. Although I had no idea what people were screaming and hooting about, I knew it was going to be something good. Running over, I was utterly dumbfounded to see them surrounding a bent sapling with the Hickory Horned Devil munching away on a leaf. I honestly have no idea how the person who found it saw it to begin with; once we were all done admiring the caterpillar, we gently released the tree. As you can see in the photo above, the caterpillar doesn't exactly stand out much, even with its size (he's in the top right). Whoever first saw it must have had incredibly sharp eyes.

As you might have guessed, the Hickory Horned Devil likes to feed on various hickory species, but, like many other caterpillars, will also feed on a variety of other trees including Black Walnut, Sweetgum, Persimmon, Buttonbush, and assorted other species.

Late in the summer, around when we found this individual, the mature caterpillars will begin to descend the trees they are feeding on in order to get ready for the next step in their life cycle. Upon reaching the ground, the Hickory Horned Devil will find an appropriate place to burrow into the soil in order to pupate. They will stay in this stage over the winter and will emerge as an adult moth either during the next summer or the summer after.

This Hickory Horned Devil was the find of the night, by far. There were many cheers and many cries of victory for this caterpillar, and of course there was also person after person taking photos of it (like Olivia Brooks in the photo above). Overall, the caterpillar night was a smashing success, and it will hopefully become an annual event!