This moth was encountered in 2010 alongside the Cannon Valley Bike Trail near the Anderson Center in Red Wing. It is a striking moth, no wonder I stopped that day to take a photo of it. Only recently did I have the opportunity to track down an ID with the help of my two most trustworthy guides: Stephen A. Marshall’s magisterial book Insects: Their Natural History and Diversity; and the indispensable website bugguide.net. What I figured out was that this moth was a Grape Root Borer Moth (Vitacea polistiformis) a spot-on mimic of the Northern Paper Wasp (Polistes fuscatus). [Note also the mimicry imbedded in its scientific name.]
I continue to be fascinated by mimicry; it’s an interesting thought experiment to figure out how this must happen. First off, I guarantee the wasp being mimicked here would make a severe and memorable snack. Second, the sting of such an experience is obviously enough to steer birds and other predators from venturing another bite at anything resembling this wasp for the rest of their lives. The result ends up being in a kind of evolutionary syllogism:
This moth looks like a wasp.
Therefore, this moth probably stings and I’ll leave it alone.
The mimics, the beneficiaries of this logic, are selected and fashioned by their survival, their color and patterning refined generation after generation. That process seems fairly straight forward. But what astonishes, I think, is the vividness and accuracy of the results.
Take a look for yourself; I’ve posted the photo of the moth as well as the wasp it mimics. If you look closely at the wings of this moth, a member of the day-flying, clear-winged moth family (Sesiidae), the large, see-through cells of the hind wings are visible as windows or gaps. Interestingly, this family of moths has not just one but many wasp mimics.
Finally, the caterpillar form of this moth is a pest to cultivated grape vines, hence its common name, Grape Root Borer.
One afternoon this last summer, while the rest of my family went boating and water skiing at my brother-in-law’s cabin on Elk Lake, I had the opportunity to visit a few wildlife refuges south of the lake scattered throughout the Sand Dunes State Forest. The dunes, that give this area its name and make it a rather unique ecosystem, were deposited at the shore of a large glacial lake. Like most dune ecosystems, this area of sandy prairie and oak savannah is extremely fragile and very little of it, if any, remains entirely intact. Still, some big efforts have been made, and are still being made, to set aside and restore large tracts of land. Having never visited any of these refuges before, I was eager to explore them.
Driving south from Elk Lake, I couldn’t help but note some similarities between this landscape and the tall-grass aspen parkland in northwest Minnesota where I had spent some time the previous summer. The possibility of discovering a remnant population of Red-veined Meadowhawks (Sympetrum madidum) suddenly fired my imagination. As I stepped from the car to explore a parcel of restored prairie, just upslope from the St Francis River, a golden-hued meadowhawk flew past me and my pulse raced as I inched toward the small bush where it had landed. For a few moments longer, fancy held the upper hand, while I allowed this dragonfly to be a female Red-veined Meadowhawk, but I finally had to concede to reality, allowing it to be a young female Variegated Meadowhawk—a look alike in some ways, but far less of a surprise, especially given the vast numbers of this species observed during spring migration earlier this year. This particular dragonfly had to be the offspring of that earlier generation of migrants. A little ways off, sharing the top of a small tree with a Halloween Pennant, another migrant made an appearance, a Red Saddlebags (Tramea onusta).
My next stop was the Uncas Dunes Scientific and Natural Area. This SNA was established in 1989, following the rediscovery of the Uncas Skipper (Hesperia uncas) in 1983, a butterfly rarity that had been found in this vicinity two decades earlier, in 1961, but had been, assumedly, extirpated at some point after that. This apparently is the case once more as I can find no record of the butterfly after the late eighties. The last record I was able to locate is an online photograph of a pinned specimen, a female collected on June 29, 1989, at the Elk River Dunes. This specimen along with another from 1967 are held at the McGuire Center for Lepidoptera and Biodiversity, Florida Museum of Natural History, University of Florida, (Gainesville, FL, USA). This segregated population, a possible relic from the post-glacial thermal maximum (ca. 8000-4000 B.P.) when major vegetation zones shifted well east of their present positions, is located many hundreds of miles east of nearest populations in South Dakota. I was visiting at the right time of year—who knows, maybe I’d get lucky…
Not more than twenty or thirty yards into the southeast unit of the SNA, I interrupted a thread-waisted wasp as it was carrying its anesthetized caterpillar back to its burrow. The startled wasp (most likely Ammophila procera given the large size of the wasp and the large size of the prey) abandoned her caterpillar and flew a few feet away where she plopped down on the sand, splayed out flat as if to hide. The caterpillar, larva of the speckled green fruitworm moth (Orthosia hibisci), lay in the middle of the trail alive but unable to move. It was very large, longer and many times heavier than the wasp. I watched for a while, taking a few photographs, but the wasp made no move to reclaim the caterpillar. However, when I returned after my walk, the caterpillar was gone, no doubt sealed carefully underground and dotted with a soon to hatch egg. Howard Ensign Evans summed it up well in Wasp Farm, “I don’t know of anything more exciting than to see a large Ammophila running over the ground with a huge caterpillar slung beneath her and then to follow her to her nest and watch the proceedings.” I had forfeited the most interesting part, being bent on finding butterflies, but still it was exciting just to have encountered this wasp.
The trail, crowded by rebarbative banks of poison ivy, shadowed by overarching oaks, led eventually to the SNA. Along the way I was bothered by horseflies and deerflies; actually more than bothered, I was bullied, badgered, and bitten to the point where looking for dragonflies and butterflies became difficult. The flies tried my nose, my eyes, my mouth, and made consistent contact with my blood at the back of my neck. I flinched at the low-buzz of a super-sized horsefly near my right ear and was pleased to see that it was really a Common Eastern Pondhawk flying off with a captured fly. I was doubly pleased when, further along the trail, several Racket-tailed Emeralds decided to tag along and nibble away at the fringes of the deerfly cloud that had amassed about my head. Another insect I was delighted to see, for similar reasons, was the white-bearded and silver-tipped robber fly, Efferia albibarbis. No doubt this large insect predator was dining on the swarm of tabanids and had a gullet full of dissolved horseflies and deerflies, or at least I hoped so.
As I walked out of the SNA, having seen no skippers, I couldn’t help but associate the shotgun-blasted ladyslipper on the scientific and nature area sign near the entrance with the slower, but more methodical violence done to the native flora and fauna of this place as it was developed and farmed over the last 150 years. And I wondered if anyone would ever spot the Uncas Skipper along this trail again.
I did, eventually, track down a few skipper butterflies. First, at a trail head north of Ann Lake, where a quick search of the parking lot and adjacent road ditches along Highway 4 yielded a few Tawny-edged Skippers (Polites themistocles) nectaring at a clump of alfalfa. Not the Uncas Skippers I’d hoped for, but nonetheless a new species for me. And then, a few miles away, in the Sherburne National Wildlife Refuge, at the canoe access to the St Francis River off Highway 1 about a mile south of Elk Lake, I caught sight of a chocolate-brown Northern Broken-Dash (Wallengrenia egeremet) nectaring on hoary alyssum in the middle of a small expanse of sandy prairie.
In that same expanse of prairie, which the canoe access trail passed through, there were also a lot of dragonflies—Eastern Amberwings, Frosted Whitefaces, Calico Pennants—and a great big surprise of a damselfly—an Azure Bluet (Enallagma aspersum). This was, so far as I knew, only the fourth time this species had been recorded in the state. Strangely the records are widespread: Albert Lea, Duluth, Webster, and now here, near the town of Zimmerman, in central Minnesota. I spent a good amount of time photographing this damsel, a strikingly blue male.
In addition to the time spent contemplating the Azure Bluet, I spent a good deal of time trying to get a good photo of a grass-carrying wasp (Isodontia mexicana) that was nectaring on the prairie flowers. This big wasp was extremely active, rarely staying put or standing still as it rooted around in the radiating white blooms of New Jersey Tea (Ceanothus americanus), pollinating like crazy.
Broad-headed bug (Alydus eurinus). These bugs are common in goldenrod fields in autumn. When I first saw this insect, moving about the grass stems and goldenrod, flicking its wings, I followed after it because I thought it was a spider wasp. It was only when it stopped and I got a good close look at it that I discovered I’d been fooled by an outstanding mimic. Not only does the adult bug convincingly mimic black spider-hunting wasps, the younger nymphs of these bugs even more convincingly imitate ants! This profile, I surmise, must provide some level of protection as they sit and siphon off plant sap with that long, needle-like drinking straw of a mouth. Should you consider collecting one, be forewarned that they also protect themselves by emitting foul smelling pheromones, well in league with the stink bugs.