INTELLIGENCE IX INSECTS 193 



Formica nifibarbis is a very pugnacious species and the odor 

 of one's hand readily provokes it to a fight. Wasmann 

 gradually trained a worker of this species, offering it honey 

 on the end of a needle, and after it came to accept the food 

 without hesitation, placing the honey on his finger where 

 it came to be accepted with no manifestation of fear or 

 hostility. 



Insects, like higher animals, learn to avoid injurious sub- 

 stances which they at first attempted to use for food. 

 Reuter placed near a nest of ants some syrup containing 

 poison. The ants partook of the syrup eagerly, but soon 

 ejected it from their stomachs; after a little they came to 

 avoid the syrup although numbers of them were commonly 

 near it. 



The ability of insects to find their way back to their nest 

 or home is developed in many cases to a very remarkable 

 degree. Bethe, possessed of the idea that insects are reflex 

 machines incapable of learning by experience, explains this 

 power in the case of ants as an instance of chemotaxis; but 

 in the bees and wasps which find their way back from consid- 

 erable distances through the air, where scent tracks would 

 not persist, he is driven to assume some mysterious power, 

 acting in a manner analagous to magnetic force, which 

 guides these insects to their goal. Ants have the instinct 

 to follow the scent tracks left by their feet in going from 

 the nest, but as Cornetz has shown, they generally do not 

 follow these at all closely, and usually return by a much 

 more direct course than the irregular path which is commonly 

 taken in their outgoing journeys for food. The power of 

 return exhibited by bees and wasps is shown pretty clearly 

 by the experiments of Lubbock, Buttel-Reepen, the Peck- 

 hams, Wagner and others to depend upon the individual 

 experience of these insects. The homing of insects takes 



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