DO ANTS FORM PRACTICAL JUDGMENTS ? 



339 



has watched this ant {Formica fasca var. subsericed) when out- 

 side the nest continue its work even when a breeze was blowing, 

 the pronounced agitation caused by such a slight draught is sure 

 to appear striking. It is, however, in harmony with observations, 

 recorded in a former paper, upon the effect of sound and light 



Fig. 2. 



upon ants. It seems that the same lights and sounds and draughts 

 which scarcely call forth any response when encountered without 

 the nest, induce quite vigorous responses when encountered within 

 the nest. In other words how an ant responds to a certain stim- 

 ulus often depends upon whether the ant is within or without the 

 nest. 



What is the cause of this crack-covering behavior ? Three 

 possible solutions suggest themselves : first, the covering of the 

 crack is a reflex activity induced by draughts through the cracks 

 affecting the ants within the nest ; second, it is a reflex response 

 caused by odors that emerge through the crack and stimulate 

 passing ants to cover it with trash ; third, it is a response due to 

 certain ants grasping the fact that the crack needed to be closed 

 and then proceeding to cover it. The last supposition predicates 

 to them what Hobhouse would call a practical judgment. 



If the first assumption be true, then all of the ants within the 

 brood chamber should have been stimulated to do the same 



