Nature: Hellgrammites, dobsonflies both fearful, fascinating

A male dobsonfly displays its formidable mandibles/Jim McCormac

(additional image at end of column)

Columbus Dispatch

July 19, 2020

NATURE
Jim McCormac

One of our strangest insects begins life in largish, powdery-white masses of eggs pasted to structures overhanging streams. They might adorn rocks, logs or even bridges. This spring, I saw dozens glued to the underside of a bridge traversing a Scioto County stream.

Eventually, odd-looking larvae bust from these natal enclosures and drop into the stream below. Known as hellgrammites, the predatory larvae will grow to formidable size. For up to three years these gilled, strictly aquatic juveniles will lurk among the stream cobble, snapping up and eating lesser beasts.

Ultimately, a hellgrammite can reach 3 inches in length. It resembles a centipede, and the business end is capped with formidable pincers. A big one, mishandled, can give an attention-getting nip.

Fierce as they are, some fish have a sweet tooth for hellgrammites and snap them up. Wily fishermen willing to work for their bait use this knowledge to their advantage.

When triggered by some reproductive cue, the hellgrammite emerges from the water and seeks a sheltered spot to form its pupal chamber. This will most likely be in moist soil under a log or rock.

After three or four weeks of undergoing a major reorganization of tissues, an utterly different looking insect will emerge.

The adult stage is known as a dobsonfly, and what a bug it is. Its body is 2 inches or more in length, and the outstretched wings might span 5 inches. Long segmented antennae wave from the head like chitinous bullwhips. The female has short but brutishly powerful pincers that can give a nip to rival the juvenile hellgrammite form.

But the male dobsonfly is truly the stuff of nightmares for the entomophobe. Its greatly elongated mandibles are about an 1½ inches in length. These scimitar-shaped appendages look like they could slice your finger off, if not eviscerate you.

It’s a male dobsonfly pictured with this column. A group of us were engaged in nocturnal field work at the Highlands Nature Sanctuary in Highland County on June 26. We had set up a series of brightly illuminated sheets that are effective at luring moths.

Many other insects are attracted to the lights, including dobsonflies. We were pleased to have the male stop by, as they are seen far less than females — probably because the males live for only three days or so, while females might live to the ripe old age of 10 days.

To test the male’s pinching abilities, I stuck my finger between its mandibles. Yawn. It did clamp down, but the long flimsy mandibles can’t generate much pressure and there was little pain. Several female dobsonflies had also come to our lights, but I didn’t try the pinch test with them. I’ll take others’ word that the girls pack a punch.

Dobsonflies tell an environmental story, and their presence can only be considered a positive. The larval-stage hellgrammites are quite sensitive to water-quality degradation. Thus, they occur in healthier streams, and good water quality is a plus for everyone.

Cool as dobsonflies are, I suppose for many people its best that they stay out of sight and out of mind.

Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature at www.jimmccormac.blogspot.com.

Male (L) and female dobsonfly/Jim McCormac

Dobsonfly: Bit of a horrorshow, this one

Ah, the legendary hellgrammite, many a bass fisherman's dream bait. This multi-legged larva looks like a mini dragon, and has a powerful set of pinchers to boot. Mishandle one of these aquatic beasts, and it'll nip you, too. I caught this one on a darter-hunting expedition in Big Darby Creek a few years back. Hellgrammites are strictly aquatic, and lurk in the substrate of streams, capturing whatever they can. Ugly as this insect may be, their presence is in a waterway is a nice thing - hellgrammites are indicators of good water quality.

If you are an entomophobe, you'll not find the dobsonfly any more appealing than its hellgrammite larval stage. Corydalus cornutus is a whopper of a bug, and males such as the one in this photo measure several inches in length.

We lured a few of these beasts to our lights last week in Adams County. We were after moths, but they're not the only critters attracted to bright lights at night, and I was pleased to spot this bruiser on the wall. It's a male dobsonfly, as can easily be told by the incredibly long scimitar-shaped mandibles (females' mandibles are much shorter). They use the swordlike mandibles for self defense, and typically fly suddenly at a person invading their space, quickly thrusting each mandible deep into the person's eyes. With an abrupt reversal of its flight coupled with a fierce jerk of the mandibles, the dobsonfly rips the victim's eyes from the sockets, and flies off to feed them to its mate.

Just kidding. Ferocious as the dobsonfly may appear, it is actually utterly harmless. While one may try to give a pinch with its mandibles if mistreated, they're too long and flimsy to gain much purchase, and would cause no harm. All visual bark and no real bite.

We were intrigued to see this Carolina mantis sneaking up on the huge dobsonfly. I watched this drama for a while, my camera's video function at the ready, hoping the mantid would attack. It bobbed, weaved, cocked its pointy triangular head, waved its legs and swayed side to side, but wouldn't get any closer to the dobsonfly than this. Fierce as the mantids are, this dobsonfly was apparently too much and the would-be predator chickened out. Can't say as I blame it.

Warblers of the Underwater World

When I first began my career, I had the good fortune to make many trips afield with Ted Cavender and Dan Rice, two of the top fish guys in Ohio. Once they saw I was truly interested in stream ecology and fish, they let me serve as labor on fields trip far and wide. In the process, I got to see nearly all of Ohio's fish, and learn them pretty well.

But that's been a while, and circumstances haven't let me look for fish in a serious way for a long time. For a few years, though, I've been threatening to make concrete plans with Mac Albin, another true fish guru, to work some riffles in Big Darby Creek. Finally, today was the day, and we couldn't have picked a better one. Warm air temperatures and low water levels made conditions for catching fish just perfect. And we're not talking Smallmouth Bass or Bluegill - oh, no, much more interesting piscine targets than those were our goal.

Our main quarry were darters. These are tiny members of the perch family, and they mostly lack air bladders and thus can't float. So one doesn't often notice darters, and you've pretty much got to make a special effort to find them. And darters truly are the warblers of the depths. At this time of year, males brighten up and their colors rival just about anything one might find in aquaria. Reds, oranges, blues, greens, you name it - darters are a rainbow palette of showiness.

Big Darby Creek, in Battelle-Darby Metropark. This 8,000-acre park protects large swaths of the Big and Little Darby Creeks, one of North America's standout river systems, and one of Ohio's most significant natural resources. More species of fish occur in these waters than any other Ohio stream, including many very rare ones.

For our subjects, we're going to have to go underwater, into rapidly flowing riffles like the one above. You see, most darters are torrent specialists, uniquely equipped to negotiate the unending rush of chutes and rapids. In some places, it is nearly impossible to find purchase and remain erect and holding a seine, so forceful is the sweep of the water. But if you can, there will be darters down there.

Mac Albin, left, aquatic ecologist for Franklin County Metroparks, and Anthony Sasson, freshwater conservation coordinator for The Nature Conservancy. They may be the two most knowledgeable people around whan it comes to the Darby Creeks, and it was a treat to spend time in the water with them. We spent about three hours working just one riffle and some assoicated habitats, and scored big time. In all, we got ten species of darters, most in good numbers. This would be like finding 30 species of warblers in one day in Ohio. For those darter listers among you, we had: Rainbow Darter, Bluebreast Darter, Spotted Darter, Tippecanoe Darter, Greenside Darter, Orangethroat Darter, Banded Darter, Johnny Darter, Variegate Darter, and Logperch.

Of course, a healthy stream has much more than darters. We dredged up this robust hellgrammite, which is the larval form of the dobsonfly. Fishermen love 'em for bait. They've got a decent pair of pinchers, and this one gave Anthony a good nip. Wish I had caught that on film!

Stonerollers, Campostoma anomalum. Fish are not easy to observe, and concerted efforts have to be made to check them out. Thus, most people don't know much about what lurks under water. These Stonerollers are males in their breeding finery. Just like birds, the males of many fish take on brighter colors and a gaudier appearance for a short while during the breeding period, which for many stream species is right now. Stonerollers are bottom-dwelling minnows, and normally don't look like much. But for a few weeks, the male's dorsal fin becomes infused with bright color, bluish-white warts known as tubercles appear on the head, and even the eye color seems to get brighter. In essence, they become real showstoppers.

Darters are aptly named. This is a Rainbow Darter, Etheostoma caeruleum, in habitat. They lack air bladders, and thus don't float. But this serves them well, and helps darters to anchor themselves to the cobble of stream bottoms in swiftly flowing riffles. There, they dart about with quick, abrupt movements, capturing an array of tiny macroinvertebrates and other stream life. Their stiff pectoral fins - fanned out to the sides in the above shot - are used as props, and help to hold the darter in place.

It isn't difficult to see how this species got the name Rainbow Darter. Breeding males are absolutely striking, enriched with bold greens, blues, and reddish-orange.

Although they appear exotic, like something that should be in a saltwater aquarium, Rainbow Darters can be quite common in appropriate habitat. Mac and Anthony seined up about 400 of them today.

Part of a male Variegate Darter, Etheostoma variatum, in breeding condition. The transition to breeding condition is triggered by water temperature. I think Mac told me that Variegates come into color when water temperatures hit about 48 degrees. This is another common species, and one that gets fairly large by Etheostoma darters standards. A whopper might stretch the tape to three or four inches. This is an extremely colorful darter; almost makes you blink and rub your eyes! Variegates are found only in Ohio River drainages in Ohio.

Variegate Darter on stream bottom cobble. Darters are especially sensitive to degradation of stream systems, as they require clear waters and clean substrates. Muck the stream up with too much sediment, and darters will vanish. Big Darby remains fairly pristine, in no small measure due to the hard work of Franklin County Metroparks and The Nature Conservancy. As Columbus and surrounding areas continue to grow, it will be increasingly difficult to protect the Darby, though. Hopefully we are up to it, and decision-makers can recognize the global significance of the stream, and its value to central Ohio.

I shot off 345 photos today, and a fair number were keepers. I'll share other underwater warblers as the week progresses, including a few of the real rarities.