The Tracking Instinct in a Tortugas Ant. 107 



to the flv. It seems that her instinctive behavior as a ''finder ant" 

 is unimpaired by her injury, but due to this injury her nest-mates no 

 longer recognize her. 



VII. It is difficult to prove that the ''finder ant" actually con- 

 ducts a swarm of her nest-mates back to the lure she has found, and 

 I tried many experiments to demonstrate or refute this hypothesis. 

 Most of these were unsuccessful, due to the "finder ant" becoming 

 indistinguishable from the numerous ants crowding around her. 

 Several instances, however, seem to give a positive result, leading 

 me to infer that the "finder ant" actually takes the lead and con- 

 ducts the swarm back to the dead fly. These successful experiments 

 were made with unusually small ants, so small that they can be 

 distinguished even among a crowd of their nest-mates, unless, indeed, 

 another equally small individual enters the swarm. These small 

 ants are only about half the size of the average worker. Moreover, 

 workers of normal size are much more numerous, outnumbering 

 these small ants perhaps 50 to 1. These small ants appear to be 

 normal in behavior, for if one of them finds a dead fly it goes through 

 with the usual "inspection," and then starts off deliberately more 

 or less in the direction of the nest. When it meets a cluster of its 

 nest-mates it rubs antennae with them, and this causes intense 

 excitement, which spreads rapidly by contact from ant to ant. As 

 soon as this is accomplished, the small ant starts back toward the 

 fly in a fairly straight course, but which is rarely or never identical 

 with the path she took from the fly to her mates. The nest-mates 

 crowd around the "finder ant," and others follow these, so that a 

 moving file of ants is seen rushing toward the fly as if an army 

 were moving along its length with the small "finder ant" in the 

 lead. Of course, if other dwarfed workers were seen in this army the 

 observation was thrown out as non-convincing; but in several 

 instances I clearly saw one of these dwarfed ants lead a small swarm, 

 composed entirely of its larger nest-mates, back to the dead fly, and 

 am thus inclined to think that it is the normal function of a "finder 

 ant" to "personally conduct" her nest-mates back to the food she 

 has discovered. 



