Strange things in trees

This post supplements my previous post, about a trip to Ollera Creek.

A nest but not the right nest

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.

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Yellow paper wasp 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.

Yellow Paper Wasp nest on Melaleuca
Yellow Paper Wasp nest on Melaleuca

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More arboreal black weaver ants – Polyrhachis dives and others

A guest post by Dr Mike Downes; his first, about a different species of black weaver ants, is here.

The subject of ant nests came up recently after an object of interest was handed in at the Museum of Tropical Queensland:

ant nest
Exhibit A
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Recycled housing

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.

Wasp approaching mud nest
Approaching the incomplete nest

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.

Wasp working at the nest
Working at the nest

Here she is again, working on the same area. No real progress is evident.

Wasp nest partly demolished
The nest mostly demolished

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.

Wasp nest in final state
The final state of the nest

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:

cocoon? 5644

cocoon? 5648

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!

Heading for higher ground

I started my monthly survey a couple of days ago by mentioning that it was raining …
According to the BoM, Townsville Airport had 36 mm from 9.00 a.m. Thurs to 9.00 a.m. Friday and 91 mm from then to Saturday morning. It was patchy, though, with bands of rain coming through, and we measured 125 mm here from Friday morning to Saturday morning. That turned the bottom of our yard (near the bananas, which love water) into a floodway. Genuine Wet-season rain!

It has prompted a couple of colonies of small ants to head for higher ground – more than a couple, I’m sure, but those I saw were both on my window-sill. One trail was outside the window and the other emerged from under the sill inside the room, and went up and over it to points unknown. The ants in both trails were so small that I couldn’t see they were different species until I saw my photos on screen.

Species 1

Ants carrying eggs
Ants on the outer window sill, one (foreground) carrying a larva and one with an egg

Not all of them were carrying eggs or larvae. Some were returning for a second load, while others were apparently just moving with the crowd.

Ants on window-sill
Fellow-travellers. The white one may be newly emerged

Species 2

Ants of the other species, coming from inside the wall, are more uniformly brown and I think they were a little smaller, though it’s hard to pick the difference between 2.5mm and 2mm when they are all moving as fast as they can.

small brown ants with eggs
Three ants going upwards, one with eggs, and one returning.

 

two small brown ants
The slightly larger ant looking back down the trail may be a soldier guarding the line of workers.

Seeing ants heading for high ground is a classic warning of more rain to come, of course. The BoM agrees: the Low in the Gulf is expected to become a weak cyclone in a day or so and funnel a lot more rain our way. But the Dove Orchids didn’t flower early last week to warn us, as they are supposed to … I’m losing faith in their reliability, I’m afraid. Or maybe they just can’t react to changes in humidity when the average is 99%.