An Myrmarachne formicaria, a type of jumping spider. An Myrmarachne formicaria, a type of jumping spider. The Myrmarachne formicaria, a type of jumping spider, is able to mimic an ant so as to avoid predators. (Photo: Wikimedia Commons)

These spiders are masters of disguise

The arachnids act like ants to avoid being eaten.

Some people become actors and can't afford to eat. Some spiders act to avoid being eaten.

It's called protective mimicry and it's meant as a defense against predators.

A team of researchers from Cornell University studied Myrmarachne formicaria, a type of jumping spider, and found it used the mechanism by imitating ant behavior to increase its chances of survival. It does this by lifting its front two legs periodically as it walks, just often enough to confuse prey into believing that its legs are ant antennae.

“Potential predators, whose visual systems are slow, cannot distinguish these stops, but do see the legs go up which, as we suggest, strengthens the mimicry show,” said research team member Tsevi Beatus, an Israeli who is now at the Hebrew University of Jerusalem.

To test how well the behavior worked, the researchers placed predators in with the spiders. They found that the predators attacked the spiders less often than usual — but about as often as they attacked real ants.

The researchers, who published their findings in the journal Proceedings of the Royal Society B, noted that the reason for mimicking ants is an obvious one because they aren't an ideal food choice for most predators. Some bite, some have chemical defenses and most belong to a nest with members that come to the aid of those under attack.

Spiders are hardly the only organism to employ protective mimicry for survival, but most do so via static physical traits (skin color, shape) rather than active ones. Which begs the question, is there such a thing as a thespiant?

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