Colonie A. eximius

Coordinated spider attack method finally explained

Bad news for arachnophobes, it seems that certain species of spiders are formidable predators. If we were so far accustomed to seeing spiders living alone, you should know that of the 50,000 known species of spiders, 20 of them live in colonies. The most impressive thing is that this small population coordinates to hunt in groups.

Among these species practicing team hunting, there is one called Anelosimus eximius. A colony of this species can consist of about 1000 individuals, and they all live on a large web measuring several meters. These spiders are particularly dangerous because when prey falls into their web, they coordinate and attack their target with fearsome efficiency and precision. This allows them to neutralize prey that they could not catch alone. It is precisely this synchronization that researchers have been able to analyze.

Raphael Jeanson, a researcher specializing in arachnids at the Center de Recherches sur la Cognition Animale (CRCA) in Toulouse, conducted the study which revealed a little more about the secret behind this impressive hunting strategy.

The secret lies in the vibration

To understand the hunting method used by Anelosimus eximius, the researchers both analyzed what was happening on the ground and used computer simulations. They placed a dead fly stuck to the end of a vibration generator on the canvas. They found that the hunting behavior was triggered by the prey’s distress movements. It would seem that the attacks are almost entirely coordinated by the vibrations exerted on the common web.

According to Jeanson, there is no leader, the spiders receive the same information at the same time and coordinate their attack in the direction of the prey.

Feel what is happening with the prey

Jeanson reports that after a while during the attack the spiders stop. The attack is in fact carried out in two stages. After receiving the signal caused by the vibration exerted by the struggling prey, the spiders begin their approach. But at a certain point, they stop for a few milliseconds to listen to the vibrations of the prey again before resuming their advance.

According to the scientists, each step taken by a spider produces a noise, and the whole colony converging on the same point will therefore scramble the signal coming from the prey trapped. So the spiders stop to “listen” to the prey to make sure they are heading in the right direction. According to the researchers, the quieter the prey, the more difficult it is for them to coordinate their stopping and starting points. If, on the contrary, the prey vibrated more intensely, the spiders would not need to stop to listen, and would be less synchronous.

SOURCE: sciencealert

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