Thigmokinesis in woodlice

Abstract 1. 1. It is shown experimentally that locomotion is influenced by external contact. 2. 2. Thigmokinetic reactions are part of the behaviour pattern and distinct from humidity reactions though their effects may be similar. 3. 3. Thigmokinetic behaviour varies with the species and with relative humidity. In general it is most marked at low humidity and in the species least adapted to land life. 4. 4. Individuals vary greatly in the intensity of their thigmokinetic responses. 5. 5. Field observations and experiments with artificial shelters show that the intensity of thigmokinetic behaviour depends on the nature of the contact both as to area and as to roughness of the contact surface. Increase in either leads to reduction of locomotion. 6. 6. It does not seem that the mechano-receptors which may be sensitive to contact are situated externally on dorsal, lateral or ventro-lateral surfaces of the segments or on the antennae. 7. 7. It is argued that thigmokinesis plays a minor part usually complementary to humidity reactions and endogenous rhythms and illumination—but sometimes opposing them—in determining trivial movements and is therefore ecologically significant. This view is supported by quantitative field observations.