Nocturnal homing in the tropical amblypygid Phrynus pseudoparvulus (Class Arachnida, Order Amblypygi).

Arthropods are renowned for their navigational capabilities, with numerous examples known from insects and crustaceans. Early studies of amblypygids (Class Arachnida, Order Amblypygi) also suggest complex nocturnal navigation, despite their apparent lack of visual adaptations to the low-light conditions of a tropical understory. In a series of two studies, we use the tropical amblypygid, Phrynus pseudoparvulus, to assess their nocturnal homing ability. Our first experiment displaced and tracked resident and nonresident individuals. Resident individuals, displaced up to 4.5 m from their home refuges and released onto their home tree, were more likely to return to their previously occupied refuge than were nonresident individuals that were collected from trees outside the study area and released at the same locations. In a follow-up study, we displaced amblypygids longer distances (6-8.7 m) from their home trees and tracked them by telemetry. These individuals returned to home trees, typically within 1-3 nights, often via indirect paths. Taken together, our results provide evidence that P. pseudoparvulus are able to navigate home, often taking indirect routes, and can do so through a mechanism other than path integration.