Spiders pay far more attention to colour than previously thought, according to new research from the University of Cincinnati.
Scientists investigated how wolf spiders reacted to videos of courting spiders when the background colour, contrast and intensity was manipulated.
They found that female spiders responded to videos of males which contrasted sharply from their background, and more strongly to the coloured versions.
In the wild, male spiders called "eavesdroppers" are known to lurk in the background and learn to mimic other male spiders' courting displays.
Biologist Professor George Uetz said: "The assumption was wolf spiders don't pay attention to colour. But we found that isn't really true."
Wolf spiders have become a popular avenue of study because of the work at Professor Uetz's laboratory into how their eight eyes function so differently to human eyes.
"We need to look more closely at the neurobiology of their eyes. We need to understand what their retinas do," said Professor Uetz.
Humans have trichromatic vision – meaning the light-detecting cone cells in their retinas can see in red, green, and blue.
Wolf spiders have dichromatic vision, however, seeing only in green and ultraviolet – and it seems that green is their favourite colour.
Professor Uetz said: "The assumption was wolf spiders don't pay attention to colour. But we found that isn't really true."
Wolf spiders are becoming a popular avenue of study because of the work at Professor Uetz' laboratory into how their eight eyes function so differently to human eyes.
"We need to look more closely at the neurobiology of their eyes. We need to understand what their retinas do," said Professor Uetz.
Having dichromatic vision "means they're basically colourblind. But they're sensitive to light in the green wavelength," Professor Uetz said.
"What we found is that for female spiders, intensity matters more than colour. But for male eavesdroppers, colour matters, too. That is the odd finding. We didn't expect that at all.
"That makes a lot of sense because when you go out in the early season when the spiders first come out, there are no leaves on the trees so there is broad spectrum light.
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"But as the seasons change, leaves come out and everything turns green. Spiders have to be able to see the contrast against a lot of colour backgrounds."
Biologists including Professor Uetz presented their findings to the American Arachnological Society in June.
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