Wasps: artists or robots?

by Matthew Cobb

[Continuing my lazy practice of re-posting material from elsewhere in the blogosphere and bringing it to the attention of WEIT readers, here’s one I posted last week over at Pestival (the insect arts festival – yes, honest!  Go look!)]

In case you weren’t listening to BBC Radio 4 at 06:15 am the other Sunday morning, I thought I would present to you the case of one of nature’s artists, the potter wasp. This small solitary wasp was the subject of the excellent Radio 4 programme The Living World. Anyone, anywhere in the world, can listen to it again here:

The female wasp makes a little clay pot about 1cm across, with a small hole in the end. She lays an egg in the pot, and then crams it full of living, semi-paralysed caterpillars which her offspring can eat. You can see quite how small the pot is in this photo from the BBC website, by Andrew Dawes. The “pot” is the tiny white thing underneath the middle finger!

[EDIT: The following (clearer) picture was taken by WEIT reader TrineBM (see comment 2 below)]:

According to Wikipedia (so it must be true, no?) the great entomologist Karl von Frisch, who was the first to study the honey bee’s waggle dance, claimed that the shape of the potter wasps’s pot inspired native American pottery designs. Quite how one could know that was true (or not) is hard to say – and what about other pots from round the world that look pretty much the same?

But is the wasp really an artist? Does it know what the pot should look like? John Walters, who’s been studying the potter wasps on this Devon heath for the last four years, says that he thinks each wasp has a different style – some pots are symmetrical, others have distinct twists. That doesn’t mean to say they know what they’re doing. Indeed, it seems certain they do not.

One of my favourite studies of animal behaviour was carried out on a potter wasp in 1978 by Andrew P. Smith, then of the University of Sydney. On the other hand, I seem to be one of very few people who rate this work – it has only been cited 13 times in the last 32 years. I feel your pain Dr Smith!

Andrew’s wasp – Paralastor – makes a rather more elaborate nest than the Devon potter wasp, a kind of odd umbrella shape, made up of a mud column and a bell-shaped entrance, leading to an underground chamber where the larva can munch its way through its living lunch, as seen here:

This picture shows the female wasp in action:

So how does she know what to build? Construction takes place in stages:

But does she have an image of what the final nest should look like? Or does she simply know that she’s carried out a series of behaviours and simply do them in sequence? The answer to both these questions is “No”.

Through a series of experiments involving changing the ground level, or altering the angle of the column, or making holes at various points, Smith was able to show that the wasp in fact proceeds by a series of steps, each of which is induced by a particular stimulus. If she sees a hole, she makes a column – even if this ends up with a bizarre double-umbrella nest:

The conclusion of the paper – apart from a lot of very tired and confused wasps – is this rather neat flow diagram, showing how the wasp decides what to do next:

So the wasp is not an artist, it’s more like a simple robot, carrying out a task when the appropriate conditions are provided. Less romantic, but still amazing!

Andrew P. Smith (1978) An investigation of the mechanisms underlying nest construction in the mud wasp Paralastor sp. (Hymenoptera: Eumenidae). Animal Behaviour 26:232-240.