Yellow paper wasps on the move

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

Hi, Malcolm,

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.

This new ‘nest’ is about 2 meters off the ground and the tree is about 4 meters from our back verandah – so I certainly hope the wasps stay there. These are the ones that swarmed on our front porch.

yellow paper wasps under porch
Paper wasps swarming under the porch

The tree was bare at 7:00am then by 1:00 pm when this photo was taken, the wasps had been busy.

Eucalypts on river bank
The location of the new nest, near top centre of the photo
foundations of a wasp nest
A closer view of the foundations of the new nest

Pat thought I lived closer to Mareeba than I do and she invited me to visit for a first-hand look, but that wasn’t possible. All I know, therefore, is what she sent me. My immediate impression was that these were indeed the Yellow Paper Wasps (Ropalidia romandi) which I wrote about here but the behaviour was new to me and the new nest (or nests) on the gum tree was (or were) puzzling.

Malcolm to Pat, 14.4.20

Hi, Pat,

I have just seen your email and photos.

If you’re not quite sure of the wasps’ identity, you could send me a close-up photo of either a wasp or the unoccupied broken nest, but if the nest is papery (not waxy) and has sheets of hexagonal cells inside an outer covering, there’s no real doubt.

I’m sorry to hear you were stung, and hope you’re over it by now. What you describe is in fact the classic way to get stung: you accidentally bump the nest and they retaliate.

I’ve never seen them “swarm” like bees but I guess it could happen if their nest was broken and they needed to re-establish somewhere else – which must happen if a branch breaks in a storm, for instance, not just from human intervention. If that’s the case, the wasps on your front porch were possibly pioneering a new nest, now abandoned in favour of the quieter location on the tree trunk. That might explain the odd pattern of construction on the tree trunk, too. If it’s possible for you to safely take a nice clear photo, I would love to see it.

The good news is that they are not aggressive as such. I’ve been living with them in my garden for years without being stung, so the nests on the gum tree and bunya shouldn’t give you any trouble. I just wouldn’t allow them to establish a nest anywhere too close to your normal activities, especially in the light of your allergy. 

Pat to Malcolm, 14.4.20

Thanks for your reply, Malcolm.

The nests are now very different on the eucalyptus  – they have about tripled in size. It’s hard to get a photo because of they built on the shady side of the trunk and have shade in the afternoon from a nearby tree, clever little things. And we see them go from one side of their nests to the other.

We are going to cut down the low hanging bunya branch this evening. We don’t see any wasps on that very round nest, but we do see green ants cleaning up. I will send you photos when I can get them done.

[Later] Here’s the nest that was vacated a couple of days ago and the green ants seem to be eating something from it. It’s about 12 cm across and was very round before the fall to the ground.

Yellow paper wasp nest, abandoned
Fallen wasp nest, with scavenging green ants
Malcolm to Pat, 14 April

Yes, that’s definitely our yellow paper wasp.

The green ants may be scavenging wasp eggs and larvae, or even the caterpillars which adult wasps feed to their young. Nothing is wasted!

Pat, 15 April

Sadly, I cannot get a better photo of the nests on the tree trunk – but they are growing very fast. I will keep trying.

If the wasps were building a cluster of separate nests close together on the tree trunk, why should they build so close together?

Malcolm, 15 April

Hi, Pat,

I assumed from what you said before that the new nesting site would become one big nest but it sounds like they are still separate. Is that the case? If so, the swarm has split and several females have promoted themselves to queen roles, which (as far as I know) is behaviour that hasn’t been recorded before. In fact, I don’t think the reconstruction of a whole colony has been recorded either.

I am curious about what’s going on but don’t worry if you can’t get a photo.

Further checking led me to Wikipedia which confirmed that colonies could split successfully and re-establish, but that females didn’t need to “promote themselves” as I had thought, since Ropalidia romandi colonies typically have many queens.

Pat, 16 April

Hi, Malcolm, This was taken in the morning sunshine, standing about 2 .5 meters away, and the nests are about 3 meters from the ground (give or take).

Yellow paper wasp nest on tree trunk
The new nest under construction

As they have swarmed before, we are quite anxious about how close they are to where we spend a lot of our time and will ask the pest exterminators to come and destroy them, or encourage them to go deeper into the woods.

We don’t want to destroy them but I recognise that multiple stings would affect me badly.

The later photos gave me a better sense of where the tree was in relation to the house, and in Pat’s position I would have had the new nest removed, too. On the edge of the lawn, not much above head height, it would have been a constant worry.

Pat to Malcolm 20 April: Last photo of nests

Got sprayed this morning. Nests were a little over a metre in length in total. All gone now.

The worker who knocked down the nest/s said that the wasps had not yet formed the cells and [what we saw] were only layers of ‘paper’, so hopefully as the majority were off foraging (certainly way fewer than the other day) they won’t rebuild there but find a place closer to the river’s edge.

wasp nest on eucalypt trunk
The last photo of the new nest/s

This last photo which Pat sent is still ambiguous but it does look more like one long narrow nest that a string of smaller ones. Either way, it was on the way to being a big colony – if, that is, the re-establishment were successful.

The rebuilding of a Ropalidia romandi colony is rarely observed so I’m really pleased that Pat got in touch, and grateful for her patience with my questions.

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