 Jumping spiders have eight eyes, the two large ones in the center-and-front position (the anterior-median eyes, also called "principal eyes") housed in tubes in the head and providing acute vision.The other six are secondary eyes, positioned along the sides of the carapace and acting mainly as movement detectors.In most jumping spiders, the middle pair of secondary eyes are very small and have no known function, but those of "Portia" species are relatively large, and function as well as those of the other secondary eyes.