Kinesthetic Sense of Insects.*

Abstract

In spite of the large number of valuable observations which have been published concerning the behavior of insects, it is rather striking that the kinesthetic sense remains a neglected factor. In recent years a new theory of geotropism has been developed by Crozier and his school. This theory is in sharp contrast to the now obsolete statolith hypothesis of orientation to gravity. It is now beyond question that in a large number of diverse organisms, including mammals and insects (Crozier, 1929), the direction of the organism in a gravitational field is determined by the body weight acting upon the “tension receptors” in the supporting musculature of the limbs. The writer (Barnes, 1929, 1930a) has shown that the angle described by an ant crawling upon an inclined surface is a precise function of the sine of the angle of inclination of substratum. The insect turns until the “pull” of the body weight on both sides of the supporting musculature is reduced below threshold value. The same phenomenon has been observed in Malacosoma larvae, in Tetraopes, and several other insects. Unfortunately we have no knowledge of tension receptors in insects, either from the physiological or histological point of view. In rats, however, the muscle tension theory of geotropism is supported by a great deal of valuable evidence concerning the histology of the vertebrate muscle spindle and the nervous discharges produced by these sense organs when stimulated by tension. The present investigation was undertaken with the hope of discovering muscle tension receptors in Arthropods. The writer (Barnes, 1930b) has recently published an account of the physiology of the tension receptors in Crustacea and the present note deals with afferent impulses from insect muscle.