Turn alternation in the pill bug ( Armadillidium vulgare)

Abstract

Summary o 1. After a pill bug ( Armadillidium vulgare ) is forced to make a turn, it turns in the opposite direction at the first choice point (turn alternation). 2. The mean angle of the pill bugs' alternating turn is a function of the angle of the initial forced turn. 3. The distance between the forced turn and choice point (5 cm, 10 cm, 15 cm or 20 cm) or between the starting point and the forced turn (3 cm or 15 cm) does not affect the magnitude of the alternating angle of those animals that alternate. 4. Turn alternation in pill bugs does not seem to be controlled by any single sensory modality. 5. Turn alternation in pill bugs appears to be mediated by a form of short-term memory. 6. The functional significance of alternating behaviour may lie in the fact that it leads to temporary orientation toward vertical surfaces. 7. The electrophysiological study of alternating behaviour could provide a means of learning something about the neurological basis of short-term memory.