Tuesday, June 18, 2013

Phenology: Buck Moth Caterpillar (Stinging Worm)

On the way to the computer center in Wise I sighed, "Will I get this chore done, or will I be distracted by the fifty-two other things that are more fun to write about than stinging worms?"

Well, under the "phenology" heading I'm entitled to mention one of those distractions: it's been a late, cool spring, and in Wise at least one dogwood tree is still blooming, as of June 17. I've never seen that in Gate City. Altitude really makes a difference; parts of the Blue Ridge Mountains really are in the same climate zone with Nova Scotia.

Right. On to the gross-outs. I saw the first Hemileuca caterpillar of the season, in Gate City, on Friday. Google shows that people further south have been living with these miserable worms for a while already...

http://wwno.org/post/make-way-buck-moths-caterpillars-above-and-below

(There's a fair amount of comedy in this radio speech. Caterpillars aren't really drama queens; they're literally brainless animals with very few nerves, and they probably do things like falling out of trees and landing on people because they don't realize they're doing these things. Stingingworms don't have to be aware that their bristles are injecting venom into human skin in order for the mechanism to work.)

But when I checked the Internet for breaking news about these animals, I found that there really is a lot of news about Hemileuca. Those of you who search the'Net for phenology posts and share and bookmark the caterpillar stories really are contributing to scientific progress. There's a lot more information about the buck moth family on the Internet than there was in field guides when I wrote my stingingworm article for Associated Content, only five years ago. In 1991 I took a stingingworm in to a government office for official identification, and all the experts could say was that it was some sort of buck moth, species unknown. Now we can look up the species on the Web.

What's a blogger to do? There's now a consensus about the number of North American species of Hemileuca (twenty-three). Most stingingworms found in Virginia are Hemileuca maia, but even for experts it's not possible to tell by looking at the caterpillar whether it's going to be H. maia or another Hemileuca species. There is not--yet--an easy-to-read web page that explains the possibilities, the similarities and differences, and what's known about coping with the different species or which of the caterpillars look alike. I can't put that page together in one day. I can share what I know about stingingworms generally, with the caveat that although all stingingworms in Virginia look and behave like Hemileuca maia some belong to other species, and get into the differences between Hemileuca species in another post.

Although the color pattern of Hemileuca caterpillars varies, note that the one in the WWNO post vaguely resembles a tent caterpillar or gypsy moth caterpillar, but it's dark along the upper back and brown on the sides. However, the easiest way to avoid confusion--and pain--is to remember that the buck moth caterpillar's hair is not furry but bristly. Tent caterpillars seem to enjoy being stroked by patient, gentle fingers. Gyps aren't especially cuddly pets, but you can pick them up if you really want to. Hemileuca caterpillars don't have to be stressed, or even aware of your existence, to raise a rash that may cause pain and bleeding for weeks.

Several small, harmless butterfly caterpillars are also covered in "modified hairs" that form branching spines. They're only trying to look like Hemileuca larvae. Most of the baby butterflies are much smaller than the Hemileucas; when they leave the tops of oak trees where they grow up, and become an orchard nuisance, Hemileuca maia are two or three inches long.

Here's a closer, grosser photo of a different color morph. If you see this image as black and white, you may be using an outdated browser, or you may be color-blind. Up close, stingingworms can be mottled in many shades of brown, purple, orange, gray, green, white, and black. I've seen many that were almost completely black. I've never seen one that looked black-and-white to me. I see Susan Ellis's specimen as black, tan, burgundy, and white:

http://insects.about.com/od/butterfliesmoths/ig/Stinging-Caterpillars/Buck-Moth-Caterpillar.htm

Here's one I see as brown, black, white, and green:

http://www.discoverlife.org/mp/20q?search=Hemileuca

Here's a sampling of the stingingworms Virginia knows and loathes...note that some of what are also sometimes called "raspberry caterpillars" have a raspberry color...

http://mothphotographersgroup.msstate.edu/species.php?hodges=7730

Close up, there are hardly two alike, although most of the ones I see are predominantly black and brown or black and gray. When I wrote an earlier version of this article for Yahoo, a web search pulled up a magnified image that filled the screen and displayed all the possible colors these animals can be, on one single caterpillar, four or five times life-size. Not something one really wanted to look at, but it did show the rich variety of the pixel-like color patterns of their skins.

Which is better observed in photos than in real life. You do not want to let one of these things live long enough to be photographed. If you see it, kill it, before it has a chance to make someone miserable.

The moths can be black and white. I see Hemileuca maia as having dark gray and white wings and red patches on the body, but at a distance they might look black and white:

http://www.butterfliesandmoths.org/species/Hemileuca-maia

Hemileuca hera [unwieldy link here] are definitely black and white moths. Here's a gallery showing the color range of moths in the genus Hemileuca: http://bugguide.net/node/view/276

Hemileuca is classified as a genus in the Saturnid or silk moth family, but they're different in several ways from the other silk moths. For Saturnids the moths are on the small side (only a two or three-inch wingspread). The caterpillars don't produce much silk, burrow into the ground to pupate (in the summer, not the winter), and emerge as moths in autumn. The moths are called "buck moths" because they fly around deer hunters' campfires.

One feature the moths have in common with other silk moths is that they don't eat. They store enough fat to live on for a few days while they fly around and find a mate. Silk moths don't have mouths. After they grow wings, mating is the sole remaining purpose of their existence and, if lucky enough to find mates before dying of old age, they take time to enjoy each other's company.

Although all silk moth caterpillars are big, fat, and repulsive-looking, only Hemileuca and Automeris io caterpillars sting. To say that they sting implies more voluntary control of their stinging spines than the caterpillars actually have. While bees and wasps have retractable stingers that they usually tuck safely inside, the caterpillars' bristles don't move, and sting whatever they touch. If they really want to, the caterpillars can squirm around and inflict more damage, but anything that brushes against them will be stung.

And although Hemileuca maia spend most of their caterpillar lives in the tops of oak trees, they have one truly obnoxious habit. A few days before crawling into the ground to pupate, they crawl around nibbling on other kinds of leaves. They are especially attracted to raspberries, blackberries, blueberries, and cherries. Although they eat the leaves not the fruit, their presence invariably produces alarm and despondency in fruit pickers.

In view of the hostility Internet sources express toward mostly harmless tent caterpillars, the tolerance these sources show toward a truly obnoxious species surprises me. Personally, living in an orchard, I think this is one of maybe two or three creatures in the world that are loathsome enough to deserve poisoning. I know poisoning is a bad strategy if you want to get rid of a nuisance species. The more of any plant or animal you poison, the more of its natural predators you lose, and thus the more undesirable plants or animals you have later. But if anything deserves a slow painful death, stingingworms do. I've been lucky enough to avoid being stung myself (in real life I say things like this with a stale comedy routine, saying "touch wood" and touching my head) but I've given tea and sympathy to fruit pickers who've touched stingingworms, and even that is enough to make a person want to chop down all the oak trees on the mountain.

The same strategy that works with the relatively tolerable tent caterpillars--pruning twigs with egg clusters on them--would work with buck moth caterpillars, except that the twigs in question are likely to be fifty feet above the ground, which makes pruning difficult.

Every little bit helps so this web site recommends, er, uh, collecting adult buck moths. Anything that procreates stingingworms looks its best when pinned to a board. During their season, one body will attract others, and the more that can be collected, the better. Moth carcasses aren't valuable but, at the end of the season, these fat moths can be useful to light a fire. (All fats blaze up quickly; be prepared.) This genus is absurdly under-predated, so the more of them we can remove from circulation, the better. The best thing about Hemileuca moths is that, like other big silk moths, their chances of reproductive success are relatively small...and collectors can make those chances much smaller.