in.] RECOLLECTION OF FRIENDS. m 



however, did not like being thus exposed ; they therefore 

 brought earth from some little distance, and built up a 

 regular wall along the open side, blocking up the space 

 between the upper and lower plates of glass, and leaving 

 only one or two small openings for themselves. This 

 struck me as very ingenious. The same expedient was, 

 moreover, repeated under similar circumstances by the 

 slaves belonging to my nest of Polyergus. 



I have also made many experiments on the power 

 possessed by ants of remembering their friends. It will 

 be recollected that Huber gives a most interesting ac- 

 count of the behaviour of some ants, which, after being 

 separated for four months, when brought together again, 

 immediately recognised one another, and " fell to mutual 

 caresses with their antennae." Forel, however, regards 

 these movements as having indicated fear and surprise 

 rather than affection, though he also is quite inclined to 

 believe, from his own observation, that ants would 

 recognise one another after a separation of some months. 

 The observation recorded by Huber was made casually ; 

 and neither he nor any one else seems to have taken any 

 steps to test it by subsequent experiments. The fact is 

 one, however, of so much interest, that it seemed to me 

 desirable to make further experiments on the subject. 

 On the 4th of August, 1875, therefore, I separated one 

 of my nests of F.fusca into two halves, which I kept 

 entirely apart. 



I then from time to time put an ant from one of these 

 nests into the other, introducing also a stranger at the 

 same time. The stranger was always driven out, or 

 even killed. The friend, on the contrary, was never 

 attacked, though I am bound to say that I could see no 



G '2 



