Potter Wasp with Prey
Sam and I found this wasp hauling her prey up the side of our house, probably to a nest up somewhere under the eaves. The wasp was pretty game about the whole business. I think the caterpillar was too big for her to fly with, and so she had to haul it back home on foot[1]. Although, I suppose it’s possible that she was just climbing the wall to gain enough altitude so that she could get airborne.
I’m pretty sure that she first stung it to death (or at least to paralysis, it wasn’t struggling at all), and then grabbed it by the neck and dragged it off.
We can get a reasonable view of the caterpillar in this next shot, but it doesn’t help much – it is one of those nondescript green ones that are practically invisible while they are on their host plant[2].
I didn’t get a very good picture of the wasp’s face, but we can see that it’s mostly black with a yellow dot in the middle.
She looks at first like one of the several kinds of yellowjackets, most of which have that distinct black-and-yellow warning coloration that so many other insects like to mimic. However, after going through this Yellowjacket ID Key from the Biological Survey of Canada, I concluded that there were no good matches among the yellowjackets. They all have too much yellow on the face and back of the thorax, and the striping on the abdomen is all wrong.
So, after backing up in the key all the way to the Family Vespidae and taking it from there, I found a better candidate. She appears to be a Potter Wasp, probably one of the wasps in the genus Ancistrocerus. Which means that she is a solitary wasp, hauling her victims back to her little mud nest. Different species make different kinds of nests, with some potter wasps making an approximately spherical mud nest about 7-8 cm in diameter. After poking around a while, it looks like the various Ancistrocerus nest in burrows in the ground[3], in crevices, and generally in whatever is convenient. In fact, this might actually be the wasp species that made this nest that Sandy found last year built in the crevice at the base of one of our windows:
When I thought she was a yellowjacket, I had prepared a whole spiel about yellowjackets to finish off this posting with. But then she turned out not to be one. Well, I should be able to turn up some real yellowjackets easily enough. So, I’ll save it for next week.
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[1] This is not the first time I’ve spotted a wasp dragging home a victim that was as big or bigger than her, but it is the first time I’ve had time to grab the camera and get pictures. I mostly see them dragging the bodies across our driveway, or across the road. The ones that resemble yellowjackets tend to like caterpillars, while the metallic blue-black ones seem to prefer grasshoppers. The most recent one I saw was on August 14, while I was bicycling to the grocery store. There was this thing that looked like a short stick, kind of scooting across the pavement. When I stopped for a look, the “stick” broke into two pieces: a blue wasp that flew off, and the corpse of a big Carolina Grasshopper that she’d killed, which was at least twice as long as her and dramatically heavier. When you find this sort of thing, the wasp will frequently drop her prey and scoot off, but if you don’t then eat the prey yourself, she will shortly come back to retrieve it and resume dragging it off to feed her babies.
[2] It actually looks a bit like this green caterpillar that I had photographed previously, except that the previous one had a black head rather than a green head. Which brings up an interesting question: that previous one turned out to be infected with parasitic wasp larvae. What if this one was also infected by parasitic wasp larvae? If the wasp feeds a parasitized caterpillar to her young, what happens? Do the parasitoids come out first, depriving her young of its meal? And if they do, are they then trapped inside the nest with no way out? Do the parasitoids end up poisoned by her venom when she stung the caterpillar? Does her young just go ahead and eat the parasitoids instead of the caterpillar? I think the whole situation could get very complicated rather quickly.
[3] Last summer, I noticed a lot of circular holes in the ground, which I thought at the time were made by tiger beetle larvae. So, I got a shovel and dug one up, traced it back into the ground about a foot by gradually breaking up the dirt clod, and then suddenly a little black-and-yellow wasp zoomed out of it. I obviously didn’t get a good look at the time, but it might have been related to this one. If I’d kept digging, I probably would have found some paralyzed or dead caterpillars that she’d stashed down there.
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Hi, Great photos. I just posted about another solitary wasp, the Great Black. Must be the season to see them about.
I am an amateur entomologist and this is one of my favorite sites. Thanks, I really enjoy visiting!
Thanks for telling me about your post on the Great Black wasp, Sheri. Based on what you wrote, I expect that the one I mentioned in the footnote, that was dragging home a grasshopper, was probably either one of them (assuming that they branch out to grasshoppers in general, and are not completely committed to katydids), or a related wasp.
I probably need to take to carrying a collapsable insect net with me wherever I go, just for when these situations come up.
Thanks, Bridget!
I wonder if an already-infected victim gives off an odor that lets the wasp knows to look somewhere else for a Happy Meal.
The other thing that occurred to me is – why don’t bugs display the same color variations as cats or even people? You do a great job identifying these critters by their marking because their markings are stable. Housecats can come out any number of colors and they’re still housecats.
Hmmm.
Hm. It could happen. It is probably to the advantage of both the parasitoid and the potter wasp for the potter wasp to avoid infected caterpillars, so such cooperative “this one’s mine!” signaling could evolve. It would be a real bear to figure out how to prove it one way or the other, though.
As for why a lot of animal species have stable, well-defined markings that can be used as species ID features, while others (like many spiders, certain lady beetles, and most domesticated animals) have markings that vary all over the place, you’ve got me. It may just be that most markings in the wild are actively selected for (either by predation or by mate selection) and so deviations are less likely to reproduce successfully (or are more likely to spin off into a different species with unique markings). But, if you have a species where the markings have no real impact on survival or reproductive success, they can become pretty random.
I would bet that the critters who don’t have color variations don’t have the genetic complexity to end up with color randomization. They’re missing a few bits in their RGB memory banks.
Oh, the intrigues! It would make for a wonderful soap opera. I hate people soap operas, but an insect soap opera would be fascinating!
More than likely, this was the wasps larvae it was carrying….they will fly with them away from the hatch location also carry them too various prepared holes too stuff them in and seal them in with mud….they also have a way of paralyzing the larvae too move it easily and too seal it in the hole…
Mark: I really don’t think that is the wasp’s larva. It has all the common caracteristics of a caterpillar (five pairs of prolegs, green skin color, head with only a few small “simple eyes”) and is somewhat bigger than the actual wasp. Plus, why would she be lugging around one of her nearly-mature larvae? If she had some place where it was able to get that big in safety, why would she want to take it somewhere else to finish maturing?
I suppose it is possible that there might be some wasps that do the kind of larva-moving that you describe (it’s a big world, after all), but this wasp is not doing it.