In a first, these crab spiders appear to collaborate, creating camouflage

Some crab spiders have ditched webs for flowers. Masters of disguise, female Thomisus guangxicus spiders blend in with petals, which allows the arachnids to nab insects that pass by while fooling wasps, lizards and birds that may munch on them. Now, scientists have discovered a male spider joining the illusionary camouflage.

The finding may be the first known example of cooperative camouflage among spiders, ecologists Shi-Mao Wu and Jiang-Yun Gao of Yunnan University in Kunming, China, report March 1 in Frontiers in Ecology and the Environment. It suggests that some organisms’ survival strategies may be more baffling than we realize, Wu says (SN: 11/20/20).

In a tea garden in a tropical rainforest in China’s southwestern Yunnan province, Wu noticed a lot of mosquitoes buzzing around a flowering vine (Hoya pandurata). Upon closer inspection, he spotted a male T. guangxicus spider that looked like pistil and stamens on one of the flowers. Wu became excited when he realized that the male wasn’t alone. “It was lying on the top of a bigger female crab spider,” he says. Wu snapped a photo and continued his field work. When he returned four days later, he still spotted the spiders together.

Many spiders spend most of their lives alone, coming together only very briefly to reproduce, says arachnologist Stano Pekár of Masaryk University in Brno, Czech Republic. “I’m talking about minutes or hours,” he says. “This is the first time that I have heard about two individuals coming together to imitate something.”

The most plausible explanation for the behavior is selection pressure, says evolutionary ecologist Thomas Sherratt of Carleton University in Ottawa, Canada. Male crab spiders must get to the flowers, where females spend most of their time, if they want any chance at mating. “But if a male doesn’t give [the] right contrast against a female, it might be easily spotted by predators,” Sherratt says. As a result, only the male spiders whose coloring complements that of females may survive. When males and females get together, it creates a joint illusion, he says.

But before drawing conclusions, more observations are needed to make sure that the observation “is not just a one-off,” Sherratt says.