Paper wasps recognize other wasps’ faces

It probably never occurred to you think that wasps have different facial features, but they do. And wasps can recognize each other. In fact, they’re more attuned to other wasp faces than they are to any other shape, including the caterpillars they eat. In fact, despite the fact that the way we see the world – and the way our brains are structured – is very different, we and wasps are similarly good at recognizing faces.

Humans and wasps appear to have independently evolved similar and very specialized face-learning mechanisms, according to graduate student Michael Sheehan of the University of Michigan, who worked with evolutionary biologist Elizabeth Tibbetts (also of UMich) on a wasp facial-recognition study. The study results were published online today (December 1, 2011) in the journal Science. Study lead author Sheehan said:

The study marks the first time that any insect has demonstrated such a high level of specialized visual learning.

Do these wasp faces look different to you? They would, if you were another wasp.

All this, despite the fact that paper wasps have brains less than a millionth the size of humans’ brains.

In their latest study, Sheehan and Tibbetts tested learning by training wasps to discriminate between two different images mounted inside a T-maze, with one image displayed at each end of the top arm of the T.

Twelve wasps were trained for 40 consecutive trials on each image type. The paired images included photos of normal paper wasp faces, photos of caterpillars, simple geometric patterns, and computer-altered wasp faces. A reward was consistently associated with one image in a pair.

The researchers found that the paper wasps, which are generalist visual predators of caterpillars, were able to differentiate between two unaltered P. fuscatus faces faster and more accurately than a pair of caterpillar photos, two different geometric patterns, or a pair of computer-altered wasp faces. They learned to pick the correct unaltered wasp face about three-quarters of the time.

Two simple black-and-white geometric patterns should have been easy for the wasps to distinguish, because the insects’ compound eyes are good at detecting contrast and outlines, Sheehan said. Yet the wasps learned complicated face images more rapidly than the geometric patterns.

At the same time, introducing seemingly minor changes to a paper wasp facial image — by using a photo-editing program to remove a wasp’s antennae, for example — caused test subjects to perform much worse on the facial recognition test. Sheehan said:

This shows that the way they learn faces is different than the way they seem to be learning other patterns. They treat faces as a different kind of thing.

Humans have a specialized face-learning ability, and it turns out that this wasp that lives on the side of your house evolved an analogous system on its own. But it’s important to note that we’re not claiming the exact process by which wasps learn faces is the same as humans.

Wasps recognize other wasps’ faces

These researchers say the ability to recognize individuals is important to a species like these paper wasps (P. fuscatus), in which multiple queens establish communal nests and raise offspring cooperatively, but also compete to form a linear dominance hierarchy. Remembering who they’ve already bested — and been bested by — keeps individuals from wasting energy on repeated aggressive encounters and presumably promotes colony stability by reducing friction.

Bottom line: Paper wasps have the ability to recognize other wasps, according to researchers at the University of Michigan. They appear more attuned to wasp faces than other shapes. Michael Sheehan and Elizabeth Tibbetts studied wasps’ facial-recognition abilities and published their work online on December 1, 2011 in the journal Science.


December 1, 2011

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