Male and female spiders pair up to look like a flower

A species of spider found in China may have evolved so that a male-female pair together resembles a flower, helping them blend in with their background.

“This may be the world’s first case of cooperative mimicry,” says Shi-Mao Wu at Yunnan University, who made the observation with his colleague Jiang-Yun Gao.

Spiders from the Thomisidae family, also known as crab spiders, are ambush predators that usually live on or near flowers.

They are known for their great camouflage abilities, which prevent them from being spotted by their prey or predators. Some species can even change their colour to match that of the flower they are sitting on.

Wu and Gao were in a tropical rainforest in Yunnan province in south-west China when a male crab spider of the Thomisus guangxicus species caught Wu’s attention. The spider was sitting on a flower of Hoya pandurata, an plant that lives on the forest’s ancient tea trees.

“When I first observed the male spider, I did not observe the female spider,” says Wu. Only when he got closer did he notice that the male spider was lying on the back of a female. “They successfully deceived my eyes,” he says.

The researchers hypothesise that the smaller and darker male might mimic the pistil – the female organs in the centre of the flower – while the female mimics the fused petals.

They only match the appearance of the flower when individual spiders of both sexes come together, the researchers say.

However, Gabriele Greco at the Swedish University of Agricultural Sciences isn’t convinced. “It is very difficult to establish the nature of the behaviour that has been observed,” he says.

In fact, during mating, it is common in many spider species for the males to stand on top of the females. “The easier explanation could be a simple interaction linked to courtship and mating,” says Greco.