Eight-Eyed Spiders Watch Videos and People

A jumping spider. The green parts are the spider's fangs. Click to enlarge this image. Elizabeth Jakob
Elizabeth Jakob

Eight-eyed jumping spiders have a near 360-degree view of the world and can be captivated by humans and nature videos.

Eight-eyed jumping spiders have a near 360-degree view of the world, according to a new study that also found these spiders can be captivated by humans and nature videos.

The study, published in the latest Royal Society Biology Letters, presents a detailed look at how each of these spiders' eight eyes works. During the experiments, the researchers also discovered that the spiders sometimes become fixated on certain nature videos, as well as people.

"Whereas many spiders, like black widows or the brown recluse, tend to avoid people, jumping spiders often seem quite fearless," co-author Elizabeth Jakob told Discovery News. "I doubt that they mistake large objects, such as people, as prey, but they are certainly interested to know whether you pose a danger."

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"If you pull a thread past one, it will often attack it, much like a cat would attack a string. They make good cheap pets!" added Jakob, a professor in the University of Massachusetts Amherst Department of Psychology and a researcher in the field of organismic and evolutionary biology.

She notes that a lot of misinformation on the Web suggests that the bite of these spiders is quite dangerous. She said that the spiders rarely bite humans and, if they do, "not much happens. I got a red spot that quickly went away."

For the study, Jakob and colleagues Lauren Spano and Skye Long showed jumping spiders (family Salticidae) videos and conducted other tests to better determine how the arachnids' vision system works. Some spiders have just two eyes, but these spiders have four pairs of eyes.

Two principal eyes face forward.

"When you look at a jumping spider, and when it looks back at you, you will notice the very large principal eyes in front," she said. "These have a very unusual structure. They have a large, fixed lens and a tiny boomerang-shaped retina that provides high resolution images and sees in both color and UV."

Jakob further explained that the retina in each primary eye sits at the back of a long, moveable tube inside of the spider's head. The spider can move these tubes in order to scan all around.

"A metaphor another researcher uses that I like is that it is almost as if the spider is looking around with a flashlight," she said.

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The other three pairs of eyes are, as a group, called the secondary eyes. They still have excellent vision, and are particularly good at detecting motion. Of these, one pair faces forward and to the side. One pair is very tiny and also faces to a side. The last pair is situated to the side and rear of the spider.

Jumping spiders not only have keen vision, but also a gregarious nature and a seemingly insatiable curiosity about humans and nearly everything else.

"If a spider turns to look at you, it is almost certainly a jumping spider," Jakob said, adding that they respond to their own mirror images and watch videos showing insects.

When shown videos of moving crickets, the spiders will attack the screen. Jakob said you "can hear the click of their fangs on the screen" as they try to chomp the virtual insects. In the wild, they stalk prey "much like a cat stalks a mouse, following it and tackling it."

Ximena Nelson, a senior lecturer at the University of Canterbury's School of Biological Sciences, told Discovery News that the conclusions of this new study "are very interesting."

Jakob and her team are now helping to build an eye-tracker to allow them to track the spiders' principle eyes as they explore images. This will allow the scientists to "get a window into the spider's brain in a way that hasn't been possible before."

Jumping spiders appear to be perfectly suited for Halloween. Aside from their arachnid ways and multiple eyes, like the fictional Dracula, they enjoy consuming blood-juicy victims, which in this case are bugs. Jakob shared, for example, that recent research found jumping spiders preferentially feed on mosquitoes that have just enjoyed a hearty blood meal.

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