In a series of experiments, under different conditions, with 3,963 woodlice, it was observed that 1) The turn alternation is manifested by the 1st and the 2nd leg on the side opposite to the first turn. The action is not related to the motion of other legs, 2) Isopods manifest an apparent behaviour of turn alternation, 3) The behaviour disappears with gradual increase in the distance between the forced turn and the free turn, 4) The turn alternation behaviour neither intensifies nor weakens with the increase of 'accurate' or 'reverse' forced turn. The behaviour is neither based on 'short-term memory' nor on the sensory input by the antennae.