Animal Behavior

Behavioral experiments have shown that the principal and secondary eyes work together to precisely target moving stimuli. For example, Dr. Beth Jakob and colleagues investigated how the secondary anterior lateral eyes direct the principal eyes of Phidippus audaxwhen tracking moving objects. Phidippus audaxwere tethered in front of an eye-tracker that recorded the movement of the principal eye retinas. When spiders with their anterior lateral eyes unmasked were shown a moving disk, the principal eye retinas moved close together and were able to track it. Meanwhile, masked spiders were unable to track moving disks with their principal eye retinas. This indicated that principal eyes can precisely target moving stimuli only with the guidance of the secondary eyes (Jakob et al., 2018). Furthermore, Cupiennius salei, a wandering spider from the family Ctenidae, has also been shown to have closely cooperating principal and secondary eyes. Cupiennius saleihave moveable principal eyes that are controlled by four muscles (Kaps, 1996) (Land, 1969). Masking the Cupiennius saleisecondary eyes reduced their principal eye movement (Neuhofer et al., 2009).