Creature Thoughts, August 2019

Wherefore Art Thou, Wasps?

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Perhaps it’s a rather odd pastime, but all summer, my family has been observing a small group of common paper wasps that made a nest between the inner glass and the outer screen of our kitchen window. We’ve kept the window closed so we can observe them without them getting into the house, and have found them to be fascinating neighbors.

We’ve watched the queens enlarge the nest, chewing up fibers into little gobs of sticky “paper.” We’ve seen the workers carry larvae in and out (as food for their own), and defend the nest against predators.

One afternoon, I spent nearly an hour watching one of the wasps fight off a small bee-like insect, which I assumed was a predator of some sort. It was determined to get at the nest, but the wasp was not going to let it happen. The insect finally gave up, and left through the gap at the top of the screen

Then, I woke one morning to find several Daddy Long-legs in the window.

And the wasps were gone.

The wasps have not returned. The nest appears to have been abandoned. I know that wasps will leave their nests before winter, but it’s only August. From what I have read, it’s common for the workers to leave the nest once the larvae pupate. The adults that care for the young are also fed by the young, which secrete a sweet substance for the adults. Once the larva cover over their cells, there is no food source for the adults, and the workers will seek food elsewhere.

The cells of this nest, however, do not appear to be covered. What happened to the larvae, which were being actively fed by the workers just the day before?

Although I have learned quite a bit about Daddy Long-legs, or Harvestmen, in recent days, I haven’t found any record of them raiding a wasp’s nest or otherwise being aggressive toward wasps. I have seen a number of accounts of the reverse, and have even watched a couple of home-video clips—wasps attacking the Harvestmen.

The Daddy Long-legs are still in the window. I’ve seen them hanging out on the nest itself, and all over the screen, sills, and frame. There are usually at least two or three in there, and also several that can be seen on a nearby tree. But not a sign of the wasps.

From what I’ve learned about the Harvestmen, it’s unlikely that they were aggressive toward the wasps. Though arthropods, they are in fact not spiders, and do not hunt like a spider. They feed predominantly on decaying animal and vegetable matter. Their mouth parts, or stomotheca, are more like that of a crab or scorpion, with short chelicerae that are used to hold on to food as they eat it. In fact, they are more closely related to scorpions or mites than to spiders.

So why, then, did the wasps move out? Was it a matter of the Daddy Long-legs moving in, and the wasps said, “There goes the neighborhood,” and just left?

Or was it that little bee-like insect? I’ve since learned that it may have been a hoverfly, which have been known to eat wasp larvae. Did it return when I wasn’t looking? Did it bring friends?

If so, why did the Harvestmen move in as soon as the wasps were gone? I hadn’t seen any sign of them previously.

It’s been a couple of weeks, and there has been no sign of the wasps. I do, however, have several happy Daddy Long-legs in my window instead.