A reader’s recent query grew into an interesting discussion and, with her permission, I have turned it into a blog post as I did with the Kookaburra story a year ago. The photos are hers, as is most of the text; I’ve just edited it lightly for clarity and continuity. My emails are in italics, while my introductory and linking text is formatted (illogically, I know) as quoted text like this.
Pat to Malcolm, 12 April
We live on the banks of the Barron River in Mareeba and I’m pretty sure these wasps are the yellow paper wasp you wrote about and put on line.
The initial nest was in a low lying branch in my front yard and I accidentally hit the branch or nest and out came wasps and I got stung. (I’m allergic, so a bit of a big deal.)
After a few days I noticed a swarm at my front porch, and although not wanting to poison them we had to encourage them to move on, and mostly they did. One tiny nest remained and my husband will remove it this evening.
But this morning on the big eucalyptus tree in our back area toward the river, the swarm looks like it is in the thousands, and building very different sort of ‘nests’ down the trunk of the white tree, a vertical row of individual pieces protruding off the tree. It doesn’t look like the usual nest but the nest in the bunya tree in our front yard (at least I think it’s a bunya – super straight, very tall and with cones) might be the same kind except that it’s about 50 feet up on the bunya.
While we were sitting in the shade enjoying a snack, we were visited by a number of small yellow and brown wasps which I immediately identified as Yellow Paper Wasps, Ropalidia romandi, and warned people about: they sting when threatened. Fortunately we were all mature enough not to react thoughtlessly when the wasps landed on exposed skin, apparently in search of moisture, and no-one was hurt; but we did look for their nest.
Some years ago I noted that I had seen yellow paper wasps, Ropalidia romandi, in my garden but hadn’t seen the nest, presumably also in my garden, which they were coming from. Its location could have been vital information, saving me from a nasty confrontation, so I kept on looking – with no success at all.
I finally spotted it very recently, above the roof-line of our high-set house in a paperbark tree (please visit this page if you want to call it a bottlebrush – it’s both) and overhanging the neighbours’ fence. A clear view of it was only possible from one or two locations even when I knew it was there, so I don’t feel too chagrined at missing it for so long.
When I saw a maroon and yellow wasp working on an incomplete mud nest, my immediate assumption was that she was building it. In the first photo in this series, one cell is about 3/4 complete and there is a dark area at the edge of the opening which is obviously wet mud.
Mud-daubers (Eumeninae, also known as Potter wasps) collect little balls of mud and stick them in place to make nests in which they lay a single egg (here and here are other species doing it). They place provisions, i.e. paralysed spiders or caterpillars, in it and then seal it and move on. Inside, the egg hatches, grows as a grub-like larva and pupates in a cocoon which it makes within the nest. It emerges from the cocoon and the nest as an adult wasp, and the life cycle begins again.
Here she is again, working on the same area. No real progress is evident.
And here is the nest a while later. By this time it was clear to me that she was not building the nest but taking it away. Why? It was some time before I had an answer, once again from the helpful folk on my Flickr groups.
terraincognita96 said, “It is quite common for Eumeninae wasps to demolish vacated mud nests of the previous season. They bring along a mouthful of water, regurgitate it on the old nest, form a mud ball and take it to their actual building site. The barrel shaped object left behind could be a cocoon of a previous inhabitant?”
So it proved when I removed it to photograph it and cut it open:
That looks like an exit hole at the top, and the lower shot shows a thin-walled cell with a little organic debris remaining inside.
In retrospect, the cocoon visible inside the incomplete nest should have been enough to tell me immediately that this wasn’t normal nest-building, but I had never heard of wasps recycling building materials before. There’s (still) always something new to learn!