INTELLIGENCE IN INSECTS 193 
Formica rufibarbis 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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