North of the Ridge

As I mentioned in my last post, in July, I spent a lot of time “hanging out” at a local pond, trying to get one real good shot of an adult Harvester. I only caught one once in the sun, and then at quite a long distance.

I never found a caterpillar, nor did I get the full-sun portrait of the adult I wanted. I did, however, get to spend about a half an hour photographing one adult that returned time and again to one well-shaded alder leaf.^[1]

But keen observers of nature will often find more than they seek.^[2]

As I was clicking away, a largish blue-black wasp flew into the picture.

I got ready for some excitement…there was none to be had.

He came and went for a full fifteen minutes. During that time, he also buzzed the aphids and the ants.

Now this was obviously a predatory wasp, so I figured it was either hunting aphids, caterpillars, or ants. I have never heard of a wasp that hunted butterflies–but I wasn’t sure.

The butterfly, the ants, the aphids–nothing showed any fear whatsoever. The butterfly seemed mildly annoyed by the constant buzzing and stomping around, but it never moved more than a couple of millimeters. The ants ignored the wasp completely. Did I mention that there were no caterpillars?

I suppose I am assuming a lot to say that the aphids were unfazed. I’m not too certain what a fazed aphid would look like.

Generally, a wasp is not something I would bother trying to identify from a photo–but this thing had white feet. I figured that those feet put an identification within the realm of the possible.

None of my field guides showed a wasp with white feet. So, I posted a picture with some friends, and I got an ID back from Bob Moul.^[3]

The wasp was a Pipe organ mud dauber (Trypoxylon politum), and they don’t hunt aphids, ants, caterpillars, or even butterflies.

They hunt spiders to store as food for their young in those nifty little organ pipe mud nests that show up on back porches and in gazebos. They are reputed to be fairly harmless (unless you’re a spider), but some people take exception to the mud nests stuck to the sides of their house, etc.

So the wasp was not hunting. What was it doing?

Not sure, but I have one, (sadly fuzzy) photo that I think might provide a clue. Just before leaving for the evening, the wasp landed and proceeded to a small drop of liquid–and drank it.

Yes, they hunt spiders–for their young. But the question is, what do the adults eat? Were they bothering the aphids for honey dew? Does the adult butterfly retain the chemical camouflage used by the Harvester caterpillar and, therefore attracts the wasp, hoping for a wee nip of aphid juice?

I certainly don’t know the answers, but if anybody out there does, I would surely like to hear from them.

Follow up: I received a nice note to the effect that yes, various wasps, yellow jackets, etc. do feed on the honey dew. In fact, it is reported that in late summer you can find colonies by listening for the hum of all the insects taking advantage of the bounty.

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1. By the way, the Alder is Smooth Alder (Alnus serrulata). Told you I would get back to you on that. [↩]
2. There, I came up with something philosophical. [↩]
3. Sadly, Bob passed away earlier this fall. I never met him in person, but I had several phone conversations with him, and we exchanged several emails. He was a kind-hearted soul, always ready to help with an ID or a suggestion. He was also a terrific photographer, and I urge you to go visit his website on PBase. [↩]

Tags: Bob Moul, Feniseca tarquinius, Harvester, Pipe organ mud dauber, Trypoxylon politum