Researchers suspect the spiders might use the resemblance to hide from prey or predators.
Scientists have discovered a unique, leaf-shaped spider that perfectly camouflages itself in rainforest trees—and even drags dead leaves up into the branches, securing them with web, to help itself hide.
A short paper published in the Journal of Arachnology this week described the spider, which was discovered in 2011 by a group of researchers in the rainforests of Mengla, in Yunnan province, China. They were on an expedition to look for spiders, but not this specific kind, according to Matjaž Kuntner, lead author of the paper and a research with both the National Museum of Natural History and the Jovan Hadži Institute of Biology ZRC SAZU in Slovenia.
"We're trained to find strands of spider silk at night by using our headlamps and we found these strands of silk and basically followed them to the source of it," Kuntner explained.
The first spider was found hanging among dead leaves that were lashed to the tree branches with spider silk, making the researchers suspect that the female spider went down to the forest floor, gathered up dead leaves, dragged them to her hiding spot, and hung them up like curtains.
"We didn't observe that behavior but I don't think there's any other way for leaves to appear on little strands of silk," Kuntner said. "The hung leaves were sort of a giveaway that it had to be a spider and one of the leaves, of course, turned out not to be a leaf at all."
The spiders are dark brown, like a dead leaf, on one side of their abdomen and light green on the reverse, allowing them to hide among any stage of the leaf cycle. Their abdomens are curved and veiny like a leaf and even have a long, stem-like protrusion that really sells the disguise. With their legs tucked up around their head, hanging from a branch, it woud be really easy to miss these creatures if you weren't a trained spider stalker like Kuntner.
Though a handful of other spiders have body shapes that resemble vegetation like flowers or twigs, this is the first time a spider that mimics a leaf has been found, Kuntner said. It could help the spider hide from predators, or to sneak up on prey, or maybe both.
A search for more specimens only yielded one other spider, which suggests they aren't that common. As the researchers wrote in the paper, "its cryptic habits and nocturnal lifestyle help evade not only predators, but also researchers."