Crafty Peruvian spider builds its own decoy « Why Evolution Is True

Crafty Peruvian spider builds its own decoy « Why Evolution Is True

Crafty Peruvian spider builds its own decoy

Don’t expect deep thoughts today, for I have writing to do!

For some reason I’ve been posting a lot of arachnids lately.  But this one is special: it weaves a web that contains a “fake spider” used as a decoy, so it’s a case of one of my favorite evolutionary phenomena—mimicry. Have a look:

A decoy spider hangs below its much smaller builder, suspected to be a new species in the genus Cyclosa. Photo: Phil Torres.

That big “spidery” thing in the middle isn’t a real spider, even though it has the requisite eight legs. It’s a dummy, woven (and with stuff added to it) by the much smaller real spider, which you can spot right above the dummy.

R prey can use deception to protect themselves against predators, this might work well causing spiders to increase exponentially in numbers until a counter mutation or counter innovation causes some predators to recognize the trick. Then those with this mutation might grow faster in numbers than those missing out on food because of the decoy.

A piece by Nadia Drake at Wired Science  explains (although leaves out some of the science):

A spider that builds elaborate, fake spiders and hangs them in its web has been discovered in the Peruvian Amazon.

Believed to be a new species in the genus Cyclosa, the arachnid crafts the larger spider from leaves, debris and dead insects. Though Cyclosa includes other sculpting arachnids, this is the first one observed to build a replica with multiple, spidery legs.

Scientists suspect the fake spiders serve as decoys, part of a defense mechanism meant to confuse or distract predators. “It seems like a really well evolved and very specialized behavior,” said Phil Torres, who described the find in a blog entry written for Rainforest Expeditions. Torres, a biologist and science educator, divides his time between Southern California and Peru, where he’s involved in research and education projects.