by Nadia Drake
Jan 21, 2014
full story and comments:
TAMBOPATA, Peru - Scientists returned to the Amazon rainforest in December to
collect data on one of their biggest finds of 2012: a spider that uses insect
corpses and jungle trash
build big, spider-shaped decoys in its web.
But these Peruvian spiders, presumed to be a new species of Cyclosa, are not the
sole sculptors of false arachnids. A second decoy spider lives in the
Philippines, on the island of Negros. Finding two spiders that make such similar
designs, 11,000 miles apart, has left scientists wondering how the behavior
evolved and if the decoys serve as lures for prey or as an anti-predator defense
system. The discoveries also suggest there may be even more sculpting arachnids.
You just have to know what to look for.
"The Philippine species and the Peruvian species, they both makes these decoys,
but the architecture is different," said entomologist
Lary Reeves, a graduate student
at the University of Florida who found the Philippine spider in March 2012. That
spider decoy's legs radiate outward from the body in all directions, while the
Peruvian decoy's legs tend to point downward.
Reeves was studying deforestation and butterfly communities on Mount Kanlaon,
near the town of Murcia, when he noticed something odd along the trail leading
down the mountain from his field site.
"I walked by this web with a spider in the middle," Reeves said. "A couple steps
past it, I realized it was a spider I hadn't seen in the area before. I
backtracked, looked, and saw that it was a decoy."
A spider decoy discovered in the Philippines. Can you spot the actual spider?
Photo: Courtesy of Lary Reeves
The decoy was about the size of a half-dollar, constructed from debris and food
carcasses, with eight legs radiating from its bulky center. It took Reeves
awhile to find the spider that sculpted the false arachnid, but he eventually
spotted it hiding in a pocket built into the decoy's abdomen. It was just
millimeters across, and well camouflaged by its building materials.
At the time, there was no way Reeves could know entomologist
Phil Torres would soon find a
similar spider in Peru, and that its artistic representations would crawl all
over the internet.
In December, Reeves went to Peru with Torres to try to learn more about these
spider-building spiders. The spiders live in an isolated patch of protected
jungle along the Rio Tambopata, in the floodplain that surrounds the
There, Reeves and Torres and their colleagues spotted about a half-dozen of the
spider-building spiders. The team photographed and measured the decoys daily,
paying close attention to how the spiders rebuilt their decoys after seasonal
rains turned them into soggy piles of web trash.
A close-up of the spider that built the decoy above. (Click to enlarge) Photo:
Courtesy of Lary Reeves
"I still think there were up to twice as many in the dry season," Torres said,
noting the relative dearth of decoy spiders in December. "There's also a
difference in how spiderlike the [decoys] are. Right after the rain, it
collapses all the legs into this mush."
That's not surprising, given how fierce the daily downpours could be. But what
Torres and Reeves couldn't solidly answer is how - and how quickly - the spiders
built their decoys.
They're planning various experiments for follow-up visits, including stationing
a video camera near one of the decoys for a 24-hour period and recording how the
spider collects and incorporates building materials into the decoy. One of the
key questions this method could answer, Torres says, it whether the spiders
leave their webs and forage for decoy ingredients, or if they simply collect
whatever falls into the web. Either way, it seems the spiders are resourceful.
"One that had recently molted had integrated his shed skin into the decoy,"
Ultimately, the team would like to gather genetic material from the spiders and
sequence it. Then, they'd like to use those sequences to understand how the
decoy-building spiders — and their crazy constructions — are related to known
Cyclosa species. Among groups of spiders, Cyclosa are well known for
incorporating debris designs into their webs. But those designs are highly
variable, and range from things like basic clumps of trash to these intricate,
spidery shapes. Do the different designs correspond with different species'
positions on an evolutionary tree? Is it possible that more complex spider
shapes are built by species that are more diverged from a common ancestor?
Genetic sequencing has the ability to answer that question, but obtaining the
permits needed to collect genetic material from the spiders has proven to be a
long - and still incomplete - process.
It's also possible that similar predation pressures have driven an example of
convergent evolution, in which both species independently found it beneficial to
construct grand, spidery illusions. Because the decoys are so large, it does
seem as though the structures are more likely playing a defensive role.
Reeves and Torres don't yet know why two spiders, a world apart, are building
decoys in their webs. But they do think it's likely that undiscovered
decoy-building spiders are sculpting false arachnids in trees all over the
"I don't think it's surprising that this happening," Reeves said. "I think that
no one's noticed in the past is surprising."
Lary Reeves and Geena Hill photograph decoy-building spiders at the Tambopata
Research Center. Photo: Ariel Zambelich/WIRED
Nadia is a science reporter who enjoys telling true stories
about planets and animals and bugs and spiders and crazy materials and...ok,
science. Her favorite moon is Iapetus.