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:
- Wasps sting.
- 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.