Visual control of refuge recognition in the whip spider Phrynus marginemaculatus.

Amblypygids, or whip spiders, are nocturnally active arachnids which live in structurally complex environments. Whip spiders are excellent navigators that can re-locate a home refuge without relying on visual input. Therefore, an open question is whether visual input can control any aspect of whip spider spatial behavior. In the current study, Phrynus marginemaculatus were trained to locate an escape refuge by discriminating between differently oriented black and white stripes placed either on the walls of a testing arena (frontal discrimination) or on the ceiling of the same testing arena (overhead discrimination). Regardless of the placement of the visual stimuli, the whip spiders were successful in learning the location of the escape refuge. In a follow-up study of the overhead discrimination, occluding the median eyes was found to disrupt the ability of the whip spiders to locate the shelter. The data support the conclusion that whip spiders can rely on vision to learn and recognize an escape shelter. We suggest that visual inputs to the brain's mushroom bodies enable this ability.