Jumping spiders zoom in with green light

Jumping spider eyes have special receptors for green light and a multi-layered retina, according to a new study.

It’s well known that jumping spiders have excellent vision, far surpassing than other spiders and even dragonflies, whose clearness of vision ranks at the top of the insect world. In a study, researchers in Japan describe how jumping spiders likely use green light and image defocus — comparing a blurry image with a focused image — to enhance depth perception, enabling them to jump with great precision on prey.

The Japanese study involved bathing jumping spiders in green and red light. Spiders in green light made very accurate jumps toward prey, while those in red light consistently jumped short of their mark.

The Japanese study looked at Hasarius adansoni, but the authors believe other types of jumping spiders share the same focusing ability. 

The scientists believe that the deepest layer of a jumping spider’s four-layer retina is sensitive to green light, while the next layer up is only partially so. This enables the spider to contrast imagery from the two layers and fine-tune its jumping distance. 

If you peer at a jumping spider closely, you’ll see it positioning its body to watch your every move with its four sets of eyes. Evidence suggests that the big eyes in front have receptors for various colors and are very sensitive to UV light.

There are approximately 5,000 described species of jumping spiders, which make up the the largest family of spiders.

Human vision is only five times clearer than a jumping spider's. Unlike human eyes, which can move to focus on something we want to see, a jumping spider’s eyes are fixed in place. Yet a jumping spider’s retina is different from ours; it can move to inspect something on the edge of its field of vision. Jumping spiders rely on vision to catch their prey, while other types of spiders rely on vibration. 

If a jumping spider should ever select your living space as its preferred hunting ground, know that many people delight in their company, describing them as “friendly” and “intelligent.” Place your hand beside a jumping spider, and it will inevitably jump aboard, saving its bite for the insects it hunts by day.