DO ANTS FORM PRACTICAL JUDGMENTS? 



C. H. TURNER. 



Scattered through the literature are several records of obser- 

 vations which indicate that ants form what Hobhouse calls practi- 

 cal judgments. However, recent comparative psychologists favor 

 the casting of such evidence out of court, because it was not ob- 

 tained from experiments conducted under proper conditions of 

 control. Lubbock 1 experimented upon the subject with negative 

 results. The first two bits of evidence reported in this communi- 

 cation are reports of mere observations ; the only excuses for 

 recording them are that the observations were made in the labora- 

 tory and that they confirm the records of similar observations 

 made by others in the field ; the third, however, is the result of 

 a carefully planned and controlled series of experiments. 



For several months I have had in one of the laboratories of 

 the University of Chicago a colony of Camponotus herculeano- 

 ligniperdus, consisting of nine winged females and about twice as 

 many workers. 2 The Janet nest in which the ants were housed 

 contained a row of three compartments (Figs, i and 2 ; A, B, C). 

 The entrance to this nest (Fig. 1, E) was about one centimeter 

 wide by two centimeters high. For several weeks no obstruc- 

 tions of any sort were placed by the ants in that entrance, although 

 a large amount of litter was kept upon the island at all times. 

 An ant usually mounted guard in the entrance E and similar 

 guards were usually stationed in the tunnels connecting compart- 

 ment C with compartment B and compartment B with compart- 

 ment A. For over two months I examined the nest several times 

 daily and in over ninety per cent, of the times I found guards 

 located in the places mentioned. 



In the course of some experiments upon an entirely different 

 problem I had occasion to fight the guard stationed in the entrance 



1 Lubbock, "Ants, Bees and Wasps," London. 



2 To prevent the experiments recorded in this paper from being invalidated by 

 mice, all holes leading into the room were filled with plaster of paris and the door 

 was kept locked whenever I was absent. 



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