48 ANTS AND SOME OTHER INSECTS. 



dispatch with which such a procession is formed in the midst of a 

 totally strange locality is almost fabulous. I repeated the experi- 

 ment in two localities, both times with the same result. The an- 

 tennae of the Ecitons are highly developed, and it is obvious that 

 their brain is instinctively adapted to such rapid orientation in 

 strange places. 



In Colombia, to be sure, I had had opportunities of observing, 

 not the temporary nests, but the predatory expeditions of larger 

 Ecitons (E. Burchelli and hamatum} possessing eyes. But these 

 in no respect surpassed the completely blind E. carolinense in their 

 power of orientation and of keeping together in files. As soon as 

 an ant perceives that she is not being followed, she turns back and 

 follows the others. But the marvellous fact is the certainty of this 

 recognition, the quickness and readiness with which the animals 

 recognise their topochemical trail without hesitation. There is 

 none of the groping about and wandering to and fro exhibited by 

 most of our ants. Our species of Tapinoma and Polyergus alone 

 exhibit a similar but less perfect condition. It is especially inter- 

 esting, however, to watch the perpetuum mobile of the antennas of 

 the Ecitons, the lively manner in which these are kept titillating 

 the earth, all objects, and their companions. 



All this could never be accomplished by a tactile sense alone. 

 Nor could it be brought about by an olfactory sense which furnished 

 no spatial associations. As soon as an Eciton is deprived of its 

 two antennas it is utterly lost, like any other ant under the same 

 circumstances. It is absolutely unable to orient itself further or to 

 recognise its companions. 



In combination with the powerful development of the cere- 

 brum {corpora pedunculata) the topochemical olfactory sense of the 

 antennae constitutes the key to ant psychology. Feeling obliged 

 to treat of the latter in the preceeding lecture, I found it necessary 

 here to discuss in detail this particular matter which is so often 

 misunderstood. 



[In his latest Souvenirs entomologiques (Seventh Series) J. H. Fabre has 

 recorded a number of ingenious experiments showing the ability of the males of 

 Saturnia and Bombyx to find their females at great distances and in concealment. 



