The Homing of the Hymenoptera 85 



ing ant. In its path place a flat piece of cardboard. 

 When the ant has mounted this, in as gentle a manner 

 as possible, transport the whole to the ground on the op- 

 posite side of the nest. The ant will leave the cardboard 

 and continue on in the direction it was going until it has 

 gone as far as the distance from the nest to the original 

 position of the card-board. There it will describe that 

 series of short complex curves, frequently made by ants 

 when in the vicinity of the nest, which Cornetz has called 

 "tournoiement de Turner." As stated above, Pieron 

 thinks that the movements of the muscles of the ant on 

 its outward journey induced a certain tension in the nerv- 

 ous system. As a result of this tension the home-going 

 ant is automatically warned when it has gone far enough. 



Without passing judgement upon Pieron *s theory as 

 to how ants determine distance, it is the contention of 

 this article that the awareness of direction is a function 

 of the perceptual peculiarities of the environment of the 

 outgoing ant. In other words, on its outward journey 

 the ant notices certain characteristics of its surround- 

 ings ; on its return trip it recognizes these and uses them 

 as landmarks. The use of the expression perceptual 

 peculiarities implies that that which guides the ants is a 

 fusion-product of more than one sense. In those ants 

 with poorly developed eyes, the olfactory (topochemical) 

 sense is basal; where the visual organs are well devel- 

 oped, sight is the sense about the recepts of which the 

 contributions of the other senses are fused. The con- 

 tention of some that we should seek a simpler explana- 

 tion is offset by the fact that there is experimental evi- 

 dence tliat ants possess associative memory. 



It is thought that the following description of how an 

 ant was taught to use an elevator on going to and from 

 a stage a few inches high is proof that ants possess asso- 



