This was written by me on August 31st 2005, when I was working at Broome Bird Observatory in northern Western Australia. I have since learned that what I called a Mud-dauber Wasp was actually a Potter Wasp.
Over the last couple of weeks a drama has been unfolding right outside my bedroom. A mud dauber wasp was busily building a nest on the back of Stu’s chair. We watched her as she hovered about with fat green caterpillars and manoeuvred them into the tiny holes in the compartments she had built. She would then plug the holes. But the chair, being a chair, got moved around a bit and eventually our poor wasp gave up after preparing two compartments.
The next morning I saw what I assume was the same wasp busily building a circle of mud on a shell outside Chris’s door. By that evening I noticed to my amazement that it was a completed compartment. These compartments give any human made pottery a run for its money with craftsmanship (or should that be craftwaspship?) Each one is wide and round at the bottom and tapers to a tiny protruding hole at the top, the sides are perfectly smooth. She brought a paralysed caterpillar for each hole and shoved it inside before laying eggs upon the unfortunate grub. She got a little ambitious one day and try as she might, couldn’t get the huge caterpillar she had into the hole. She built about a 5 compartments – approximately one a day until she was done. I thought that was it.
The next day she was still flying about and I noted that she was building up an outer wall of tiny clods of mud. In the end she created a rounded dome of mud over the compartments inside. This dome is nowhere near as smooth sided as the compartments – it’s built for defence, not beauty. Inside this fortress her young can hatch and munch upon a fresh caterpillar – they are paralysed, not killed – and take the time to peacefully metamorphose into adult wasps before breaking free and continuing their own lives. For a few days the mother wasp hovers around and sees off anyone who looks too close.
That was about a week ago. Mother wasp has obviously decided her babies are safe inside her fortress and has gone off to do whatever mud-dauber wasps do after laying eggs. This morning I noticed a small hole in the top of the dome. The telltale sign of the cuckoo wasp. Later this afternoon we saw her in her metallic green-and-blue glory going about her work.
The cuckoo wasp digs a perfectly round hole in the nest of the mud-dauber, deftly removing the hardened mud. She then uses a long ovipositor to lay an egg in one of the compartments next to the egg of the mud-dauber wasp. We watched as she dug, then turned around and laid her eggs. Once her egg hatches it will eat the caterpillar stored for the use of the mud-dauber larvae. It may even eat the mud-dauber larvae itself. Either way, the mud-dauber loses.
An industrious Potter Wasp.
A conniving Cuckoo Wasp.