210 INTELLIGENCE IN INSECTS 



spreads like a conflagration till it has seized on most or all 

 the members of a community." It is in their attacks upon 

 enemies that imitation in ants is especially marked. An 

 attack by an ant is the signal for others to join in the fray. 

 Sometimes a strange ant may be tolerated in a nest until 

 it happens to arouse the animosity of one of the members, 

 when various others fall to and help to dispatch the intruder. 



Wasmann states that several beetles of the species Dinarda 

 dentata were received as guests in a nest of Formica sanguinea 

 and had lived there for some time and propagated. He 

 then placed in the nest a specimen of an allied species of 

 Dinarda which was attacked and killed. This aroused the 

 killing propensities of the other ants which fell upon the 

 Dinarda dentatas, and the guests which had been kept for 

 so long met their fate. That ants in their treatment of 

 aphids are influenced by imitation is indicated by the fact, 

 signalized by Forel and Adlerz, that Formica sanguinea, 

 which very rarely make use of honey dew as food, readily 

 adopts the custom of its slaves upon perceiving them solicit 

 the aphids for their sweet exudation. Slave making ants 

 readily adopt guests which are received in a friendly manner 

 by their slaves, although they would otherwise be apt to 

 attack them, and slaves in turn are disposed to be friendly 

 to the guests which they perceive to be tolerated by their 

 masters. 



In treating of insect intelligence we shall find it instructive 

 to consider its failures as well as its exceptional manifesta- 

 tions. As Forel has remarked insects are exceedingly stupid 

 as regards everything not closely related to their instinctive 

 interests. But even when the latter are involved, they 

 usually fail to make the simplest and most obvious inferences. 

 A striking case is furnished by the Amazon slave-making 

 ant, Polyergus rufescens, which on account of the remarkable 



