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.
It is about the size of a rockmelon, and the telephoto lens shows the wasps moving in and out through well-sheltered openings, as in the larger nest I saw recently at Turtle Rock.
Life cycle and nest construction
Just so that we all know who we’re talking about, here’s one of my older photos of a single wasp:
The nest is made entirely of a papery material consisting of plant fibres glued together with salivary secretions, as this scientific paper explains. Inside the outer envelope of an abandoned nest (do not try looking inside an active nest!) we find a stack of horizontal combs separated and supported by short pillars.
The similarities to bees’ hives are obvious. In fact, Yellow Paper Wasps are more “social” than our other paper wasps, with bigger nests which are able to continue from year to year even in climates unfavourable to year-round activity. A Japanese researcher, J. Kojima, has found that colonies can switch from growth mode (lots of larvae) to maintenance mode (fewer larvae, more stored nectar) according to the availability of food.
Kojima saw this behaviour in colonies on the Atherton Tablelands. It is probably important, too, in SE Queensland (where nests a metre long are reported) but I’m not sure whether it is so necessary here. There’s always more to learn!
There’s always more to learn, as I said when I published the post a fortnight ago, but these afterthoughts might as well go here rather than become a whole new post.
Firstly, nest size.
This abandoned nest was found in the University gardens and passed on to me. It’s not a metre long but it’s more than halfway there – about 600 mm, in fact – and it’s not exceptionally large for our area.
Nests of green ants and these paper wasps are both arboreal, are both made of vegetable matter, and are roughly the same size. I know immediately which of them I’m looking at, but hadn’t thought about just how I know.
- Green ants construct their nest by stitching together whole green leaves. Some of them later die, but the outer layer of an active nest still usually has green leaves in it. Paper wasps, on the other hand, construct their nest of chewed leaves, so the outside is nearly always pale brown and rather smooth. The exceptions occur when expansion of the nest leads to incorporation of nearby foliage, as in both of the smaller nests on this page.
- Paper wasps like to build their nests on a solid support, usually a tree trunk but sometimes a rock (e.g. the one at Turtle Rock which I mentioned earlier) or, I guess, a house wall. Green ants usually build on the lightest, leafiest twigs because they are easier to pull together.
- A consequence of (2) is that wasps’ nests are usually well shaded but green ants’ nests are often in full sun (you can see an extreme example here). The nest featured at the top of this post is therefore somewhat unusual in being so exposed, although I have sometimes seen others near the ends of branches.
Here’s a green ants’ nest by way of comparison.