The paper wasp cultivates difference

A paper wasp builds a nest from wood fibers it has chewed into pulp on April 24, 2020 in Montlouis-sur-LoireGUILLAUME SOUVANT

The paper wasp has just entered the very narrow circle of animals thought to be capable of forming an abstract concept, such as that of the similarity or difference between two things.

Most species know how to distinguish the essential from the otherwise, such as good fruit from bad fruit or the cry of a conspecific from that of a predator. Very few are able to form an abstract concept like “equal/not equal” and apply it to different situations.

Aside from primates, few species have such a gift, including corvids, pigeons, parrots, dolphins, and ducklings. In invertebrates, it is only listed in the European honey bee.

We must now add Polistes fuscatus, the paper wasp, according to the study published in Proceedings B of the British Royal Society on Wednesday.

This social insect is known for its ability to accurately distinguish the faces of its conspecifics. A team of neurobiologists from the American University of Michigan studied its ability to do better.

First, they “taught” the wasps to associate a pair of similar or dissimilar images or smells with a harmless but unpleasant electric current, and the opposite pair with the absence of a shock.

Each wasp was in a cube whose walls, for example, bore a pair of identical colors. She stayed there for two minutes and was subjected to an electric current transmitted through the floor, then after a one-minute pause she was placed in another unpowered cube where there were a pair of different colors.

– Less than a million neurons –

The pairs of stimuli, colors, wasp faces, or smells, were rotated between sessions so that the animal did not associate any particular pair with the electric shock.

After four learning units and a break of three quarters of an hour, the wasp was subjected to a test to check whether it had integrated the term “same/not the same”.

She was placed in a box where she had the choice of moving to a limb bearing an identical pair of stimuli or to a limb bearing different stimuli. The correct choice is to move towards the pair of stimuli which, in his experience, is associated with the absence of an electric shock.

First, the type of stimulus – color, face, or smell – was identical to the learning phase, but not the stimulus itself, for example, the color changed. After ten trials and another break, the trial was repeated with a type of stimulus the animal had never encountered, such as the smell of the paints.

In both cases, the wasp passed the test with more than 80% success, well beyond luck. A result that is completely independent of the type of stimulus.

And a feat considering that this wasp’s brain, like that of the European bee, has fewer than a million neurons, while that of the pigeon exceeds 300 million and that of the macaque 6 billion, the researchers note. And that leads them to suspect that learning the concept of “same/not same” may be more common among insects than previously thought.

In addition, they conclude that the “miniature insect nervous system sets no limits to the sophistication of their behavior,” the study states.


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