Ants Correctly Locate the Zero in a Continuous Series of Numbers

Knowing that the workers of the ant Myrmica sabuleti have a concrete notion of zero, and that they can expect the time and the place of the next delivery of food, we experimentally examined if these ants could locate the zero at its due cardinal place. The ants were visually trained step by step to a continuous decreasing series of two amounts of elements differing by one unit, and of which, at each step, either the lower or the higher amount was associated with food. The ants were tested at each step of the decreasing series, and each time essentially reacted to the amount of elements which would be associated with the following food delivery. This showed that the ants could distinguish amounts of elements as being lesser or higher by one element, up to and including the absence of element (the zero). At the end of the series, the ants perceived the zero as being ‘1 element less 1’ as well as 1 element as being ‘0 element plus 1’. They thus correctly located the zero at its due cardinal place.