53 6 ANTS. 



soon conic to have the same significance to the observer as the charac- 

 teristic attitudes and cries, or what have been called " the expressions 

 iif the emotions " in our domestic animals. Of course, all the signs or 

 signals employed by ants and other animals in conveying their impres- 

 sions to other members of their respective species are concrete and 

 instinctive, or what Uergson calls "adherent," and not "movable" or 

 rational signs like those of language and mathematics. 



4. Imitation and Cooperation. These are very closely connected 

 with communication, for the object of much of the interchange of 

 impressions in an ant colony is to secure cooperation through imitation. 

 This is clearly observed in the carrying out of foraging expeditions, 

 like those of the slave-makers and Dorylines, in bringing in large and 

 unwieldy booty, in the removal of the brood when danger threatens, 

 in the construction of nests, aphid-tents and covered ways, in defend- 

 ing the colony against intruders, in storing seeds in particular chambers, 

 in building and cultivating fungus-gardens, in restraining the males 

 and females from leaving the nests for their nuptial flight till the pro- 

 pitious time arrives, etc. Many of these activities can be studied in 

 artificial nests. Under such conditions one usually sees a particular 

 activity started by one or a few workers, which have more initiative 

 or respond more quickly to a change of conditions than the great bulk 

 of the colony. The movements of such individuals attract the atten- 

 tion of others in their immediate neighborhood and these forthwith 

 proceed to imitate their more alert companions. Then the activity 

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

 of the community. Imitation and cooperation of this description, which 

 is really a form of learning by experience, is best seen in a colony that 

 is moving into an artificial nest placed in the Forel arena or on a 

 Lubbock island (see Appendix A). Sometimes it is difficult to decide 

 whether a particular change of condition has simultaneously stimulated 

 a great number or only a few workers to perform an appropriate reac- 

 tion. Such doubtful cases are most liable to arise when the stimulus 

 acts continuously and for a long time, as when a colony is situated in 

 an unfavorable locality, or in one that makes it necessary to construct 

 a peculiar form of nest. Then it may be doubtful whether the nest 

 modification is initiated by one or a few workers that are imitated by 

 the remainder, or whether all or nearly all the workers simultaneously 

 alter the style of architecture. Even in such cases, however, I am 

 inclined to regard the former supposition as the more probable. There 

 has been much discussion as to whether or not cooperation among ants 

 extends to the succoring of companions in danger or distress. Renter 

 (1888) claims to have found positive evidence of such acts of sym- 



