n, pl. The simple eyes of a spider, usually numbering eight. They may be arranged in two or more rows of two to four eyes. In some hunting spider families, like the salticids, the foremost central eyes may be modified with a movable retina to achieve binocular vision and range estimation. All other ocelli may be simple motion or light detectors. Among spiders with eight eyes they are usually designated in pairs as the anterior medians, the anterior laterals, the posterior medians and the posterior laterals; with six in pairs they may be called the anteriors or the two pairs of laterals. The relative size, placement and color of spider eyes are important in identifying spiders.