Peruvian Spider Builds Spider-like Decoys

A potentially new species of spider that builds spider-resembling assemblages of debris onto its web has been discovered in the Peruvian Amazon Rainforest by a research expedition led by Phil Torres of the Peru Nature blog. One should be cautioned from thinking that this is the sudden realization of a particularly cognizant spider, however -- the genus, Cyclosa, is known to be fond of clumping trash to their webs. Years of generations of spiders doing this in slightly different ways would be able to stumble, through trial and error, upon a symmetrical pattern of debris that resembles the shape of itself. And as a by-product of this experimental behavior, spiders with trash clumps that look more spider-like are that much less likely to be attacked by predators that are conditioned to recognize the distinctive pattern of a spider and instead attack the decoy.

Phil Torres

The spiders left over from the successful survival rate increase that the spider-shaped decoy affords them from predators continue to pass on this behavior to their offspring while non-spider-shaped-decoy-using spiders are more likely to be killed before reproducing.

Writes Torres:

From afar, it appears to be a medium sized spider about an inch across, possibly dead and dried out, hanging in the center of a spider web along the side of the trail. Nothing too out of the ordinary for the Amazon. As you approach, the spider starts to wobble quickly forward and back, letting you know this spider is, in fact, alive. 

Step in even closer and things start to get weird- that spider form you were looking at is actually made up of tiny bits of leaf, debris, and dead insects. The confusion sets in. How can something be constructed to look like a spider, how is it moving, and what kind of creature made this!?

It turns out the master designer behind this somewhat creepy form is in fact a tiny spider, only about 5mm in body length, that is hiding behind or above that false, bigger spider made up of debris. After discussing with several spider experts, we've determined it is quite probable that this spider is a never-before-seen species in the genus Cyclosa. This genus is known for having spiders that put debris in their webs to either attract prey or, as in this case, confuse anything trying to eat them. 

You could call it a spider decoy, in a sense. The spiders arrange debris along specialized silk strands called stabilimenta in a symmetrical form that makes it look almost exactly like a larger spider hanging in the web. Studies have found that some Cyclosa species have a higher survival rate against potential predators like paper wasps because the wasps end up attacking the debris in the web rather than the spider itself. As seen here, Cyclosa can make debris look a bit like a spider, but not nearly as detailed as the spiders found at the Tambopata Research Center which have a complex form that actually looks like a bigger version of themselves, complete with legs and all.

The potential species is not yet named. "It takes a lot of time and effort to go from finding [a potential species] in the field to actually describing it. Specimens will have to be collected to compare to known species, dissections done on identifying features like the genitalia, and descriptions will have to be written to show why this species is different from others,  a type specimen will have to be selected, and the eventual publication of all of that information in a journal. Only then can it be considered a named new species to science," Torres writes.