GEOTROPIC ORIENTATION IN ARTHROPODS : I. MALACOSOMA LARVAE

The geotropic orientation of caterpillars of Malacosoma americana during progression upon a surface inclined at angle alpha to the horizontal is such that the path makes an average angle theta upward on the plane, of a magnitude proportional to log sin alpha. More precisely, the product (sin alpha) (sin theta) is constant. This is traced to the fluctuation of the pull of the head region upon the lateral musculature of the upper side during the side to side swinging implicated in progression.