54 ANTS. 



wherefore," to use Llo\d Morgan's expression, for a mere association 

 of sense impressions is not deducing conclusions from premises. There 

 are in the literature, however, many startling accounts in which ants 

 are described as reasoning like human beings, or as acting in such a 

 manner as to make any other interpretation of their behavior seem 

 impossible. These accounts may be separated into two classes ; those 

 involving a demonstrable misinterpretation of facts and those whose 

 main or only value at the present time is to suggest lines of experi- 

 mental investigation. In the first class belong such cases as the 

 following : 



Several writers have described ants as building earthen bridges over 

 sticky bands that at first prevented them from climbing trees (Leuckart ), 

 over water moats surrounding their nests (Turner, 19075), or over the 

 surface of honey placed in their nests ( Ern. Andre, 1894). In each 

 of these cases the observer, a trained zoologist, regarded the act as due 

 to reasoning, or, at least, as the result of a "practical judgment." In 

 reality, however, nothing more than a reflex or simple instinct was 

 manifested in any of these cases. If the observers had had a more 

 intimate acquaintance with ants, they would have known that the>e 

 insects almost invariably throw earth, empty cocoons, or particles of 

 debris on any liquid or viscid substance in their immediate environ- 

 ment. Such actions result in covering the whole surface of a small 

 amount of liquid, so that the ants are able to cross over to the other 

 side on what was never intended to be a bridge. That this is the true 

 interpretation of the foregoing observations is shown by experiments 

 like those performed by Wasmann. He placed near a nest of Formica 

 sanguined a watch glass full of water, with a number of pupa on an 

 island in the middle. The ants threw sand into the water till they had 

 made a bridge to the island and then carried away the pupae. Later 

 he placed near the nest a watch glass full of water, but without pup;e, 

 and the ants filled it with grains of sand as before ! The significance 

 of this reflex or simple instinct which may be observed in any artificial 

 nest in which the ants are provided with liquid food and a little earth 

 or detritus, is not altogether clear. Escherich ( 1906) interprets it 

 as an instinct of cleanliness, but I am inclined to believe that it repre- 

 sents an effective method of dealing with water that may soak into 

 the galleries of the earthen nests during showers. 



Another case that has been interpreted as an example of reasoning 

 is the behavior of the fungus-growing Aita se.vdcns queen while she 

 is founding her colony, and of the workers of this species during inun- 

 dations. These are such complicated bits of behavior that von Ihering 

 ( 1898) can scarcely be blamed for saying that the insects are " fully 



