A wasp never forgets a face

A wasp never forgets a face
By Science Online’s Clare Pain

Posted December 02, 2011 21:06:04

A female Poliste fuscatus paper wasp. Photo: Being able to visually recognise faces makes sense living in a situation with multiple queens. (Science/AAAS)
Map: United States

Primates have a face recognition system that enables them to distinguish between individuals, and now it seems some wasps do too.

But the new study has also found wasps are likely to have evolved their ability quite separately and it may work in a different way.

Michael Sheehan, a PhD student at the University of Michigan in the USA, and his supervisor, Dr Elizabeth Tibbetts, report their discovery in the latest issue of Science.

“We know that the same area of the brain in other primates does the same thing and it’s also the same brain area in sheep”, Mr Sheehan said.

“But as far as I’m aware, our work is the first example of face recognition in an invertebrate – certainly in an insect.”

Mr Sheehan studied two closely related species of paper wasps that live in Michigan and found one could recognise faces while the other could not.

“The two species are essentially the same in all aspects – they even build nests next to each other,” he said.

“They only differ in the number of queens in a nest.”

The species that could recognise faces, Polistes fuscatus, founds nests containing multiple queens – typically three or four queens but sometimes as many as eight.

The other species, Polistes metricus, has nests with only one queen.

Being able to visually recognise faces makes sense with living in a situation with multiple queens.

“There is a linear dominance hierarchy”, Mr Sheehan said.

“The top queen does lots of reproduction and not much work. The queen at the very bottom of the hierarchy does lots of work and not much reproduction.”

He believes wasps need to be able to recognise the different queens.

The scientists already knew that the P. fuscatus wasps could recognise each other, but they wanted to know whether the wasps were using a special face recognition system to do it.
Escaping the buzz

Mr Sheehan captured wild queen wasps from nests of both species to test in an experiment.

The wasps had to crawl through a T-shaped maze in which the floor was slightly electrified, except for a ‘safe area’ in one of the arms.

When the wasps reached the junction of the maze they had to choose between left or right, not knowing which side the safe area would be on.

Rather like signs at a road junction, Mr Sheehan put a different picture of a wasp face on each arm. One face was associated with the safe area.

Between each trial, the safe area was moved randomly between the arms, so the wasps needed to ‘read the sign’ to make the right decision at the junction.

The P. fuscatus wasps rapidly learned which face meant safety, but the P. metricus wasps did no better than chance.

Mr Sheehan then repeated the experiment using signs consisting of simple patterns instead of faces, and also tried pictures of different caterpillars, which are the wasps’ main food source.

Both species of wasp learned to read the pattern and caterpillar signs equally well.

But for P. fuscatus, success was much better when the signs were faces.

“Their overall performance is more accurate and their rate of learning is faster [when they are using faces]“, Mr Sheehan said.

He believes this is evidence faces are being detected by a special face-processing system.
Antenna cue highlights different system

Further evidence for a special system is that the wasps cannot recognise digitally altered photos of wasps with their antennas removed.

“It’s as if the antenna cues the wasp [that it is dealing with a face]“, Mr Sheehan said.

Dr Romina Palermo of the Australian National University in Canberra says there is no real parallel to the antenna cue in human face recognition, which suggests the wasps may be using quite a different system.

“In terms of being able to understand the evolution of face recognition this work is important”, Dr Palermo said.

“The brains of humans and wasps are very different.”

She thinks it is interesting face recognition has evolved in the species where there is cooperation between queens, and she wonders which came first -cooperation or the ability to recognise faces.

“The next step is to figure out the similarities and differences between the human and wasp systems”, she says.

Mr Sheehan believes face recognition has probably evolved several times and thinks it is striking that there is such a dramatic difference in face recognition ability between two very closely related species of wasp.

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