A Direct Response of the Crab Carcinus to the Movement of the Sun

ALTHOUGH it is at first sight unlikely that a crab should take note of the direction of the Sun's movement directly, two lines of evidence already suggest this conclusion. Crabs follow with their eyes the movements of a striped drum which is revolved around them at speeds even lower than one revolution per day1, and several species of lower Crustacea2 as well as the Pacific shore crab Hemigrapsus3 utilize some feature of the path of the Sun as a basis for directional escape movements in relation to the local direction of the sea.