Some species of cave-dwelling spiders lack eyes but still maintain the ability to sense light, which likely protects them from the arid environments at the sunny mouths of caves

The dark depths of southwestern China’s cave systems are patrolled by pale spiders smaller than a Tic Tac. Like many other cave creatures, these arachnids sport noticeably undeveloped eyes. Some lack eyes altogether.

But new research shows that these cave spiders don’t turn a blind eye to light. In a study published on Wednesday in Science Advances, researchers found that even cave-dwelling spiders that lack eyes entirely can still sense light. This vestigial “vision” may help the spiders, which thrive in damp conditions, steer clear of bright cave openings that lack moisture.