Jumping Spiders Have an Eye for Everything

Jumping spiders have square heads, with four pairs of eyes on them, and thus 360 degrees vision. Until now scientists thought that the largest pair in the front of their head is used for stalking prey, color vision and distinguishing shapes, and the other three pairs are much like the human peripheral vision.

Australian animal behaviorist Dr Ximena Nelson, from Macquarie University in Sydney along with her colleagues studied the jumping spider's vision and discovered that the anterior lateral eyes do not only detect motion. Their study was published in the current number of the Journal of Experimental Biology.

In their experiment, they used the Servaea vestita spider, living under gum trees in Australia. They covered all of the spider's eyes except the AL eyes (eyes that are also on the front of the head) and noticed its behavior. The spider clearly made a distinction between things that needed the main eye's attention and things that did not. It is only logical that the spider does not react to everything that moves. “If they were to orient towards every shadow of a moving leaf, they'd be pretty tired half an hour after they'd got up”, said Nelson.

Researchers noticed that it's AL eyes reacted mainly to dots that had the speed and size of potential predators, or prey resembling the tethered house files. Some spiders even attacked, having only the AL pair of eyes available, thing that amazed scientists. They also noticed that females were much more receptive than males, are were more likely to respond.

Nelson and her team say that they now understood that spiders have sets of eyes for specific tasks. And the anterior lateral eyes may nor be as effective as the main pair, Nelson claims they are “good enough” and she calls them “not-so-secondary eyes”.