Studies in Diurnal Rhythms

Abstract

A composite diurnal locomotory rhythm has been established in the woodlouse Oniscus asellus. This is correlated primarily with alternating light and darkness, and not with fluctuating temperature or humidity. The intensity of the humidity response of the species is less in darkness than in light, and less still in darkness when the animals have been kept in darkness for some days previously. It increases with desiccation. The response to light is greater, too, in animals which have been kept in darkness for some days, and these tend to remain photo-negative in dry air whereas controls become photo-positive with desiccation. The sensitivity to carbon dioxide is much greater in animals from a culture kept in darkness than it is in controls. The results obtained are discussed in relation to the nocturnal ecology of the species.