Males are equipped with a furry, red colored ‘crown’ and legs. But he probably isn’t even able to admire his own colorful splendor.

Animals use colors in many ways. Think camouflage, intimidate rivals or attract partners. However, it is not always clear what bright colors can mean. Because what exactly is the function of the red-colored ‘crown’ and legs of the jumping spider saitis barbipes? Researchers are confused about it. Because this spider turns out not even to be able to perceive its own red hues.

saitis barbipes
saitis barbipes is a common jumping spider in Europe and North Africa. You can find it in Mediterranean areas, for example, on houses and rocks. The females are brown in color, while the males have many colors when viewed from the front: green eyes, black stripes on the white front legs and a red color above the eyes. The larger hind legs are red near the body and transition to black with white tips. Initially, it was thought that males used their impressive red colors to seduce a female. But it turns out there is more going on.

Study

In a new study researchers decided to demystify what saitis barbipes actually see exactly. “We assumed they use colors for communication,” said researcher David Outomuro. “But we didn’t know if they can see those colors themselves with their visual system.” The researchers collected spiders from Slovenia and wanted to know whether they have certain light-sensitive or color-sensitive photoreceptors. It leads to a surprising discovery. Surprisingly enough, the researchers found no evidence for a red photoreceptor. So the reds that are so vivid to us are probably just dark spots to the jumping spider.

Color-blind

It means that the very colorful spider is surprisingly color blind itself. He is not even able to admire his own colorful splendor. Instead of the vivid red we see on its face and legs, the jumping spider may be seeing a kind of dark green instead of red. And that also means that saitis barbipes its colorful appearance may be used for a purpose other than attracting females.

Color contrasts that may be visible to the male jumping spider saitis barbipes (left) compared to birds and humans (right). Instead of the vibrant red we see on its face and legs, the jumping spider may be seeing some sort of green. Image: Mateusz Glenszczyk and Cynthia Tedore

What’s going on here? The researchers suspect that the saitis barbipes manages to camouflage itself well with its red and black colours. Predators that do perceive red, he puts on the wrong track. That’s right. “The red and black colors blend together to form an intermediate, orange, brownish color,” explains researcher Cynthia Tedore. “This helps the spider to blend in better with its habitat – which consists mainly of leaf litter – than a completely black color would.”

sunscreen

According to the researchers, this discovery reminds us how animals sometimes perceive the world in a very different way than we do. You can compare this a bit with our own use of sunscreen. Sunscreen absorbs ultraviolet light extremely well. But we actually notice quite little of this ourselves, because we cannot see that spectrum. “If aliens were studying us, they might wonder why we paint our bodies with highly UV-absorbing colors when we lay down on the beach,” said study researcher Nathan Morehouse. “We can’t see ultraviolet light ourselves, so we have no idea we’re glowing in ultraviolet when we apply sunscreen.”

The results show that nature continues to amaze us. “We thought colorful spiders could see a lot of color,” Outomuro says. But that is certainly not always the case. “Animals can experience the world in ways that are completely foreign to us,” concludes Morehouse.