106 The Tracking Instinct in a Tortugas Ant. 



carried through the air, the "finder ant" becomes incapable of con- 

 ducting a return swarm to the fly. Indeed, it appears probable 

 that the ''finder ant" has lost its sense of orientation, for if we brush 

 up an ant from the midst of the crowd moving in the neighborhood 

 of the nest-crevice and carry it through the air to a dead fly, say 

 8 or 10 feet away, the ant "inspects" the fly in a normal manner, 

 but instead of starting on a fairly straight path back to the nest- 

 crevice, it courses widely over the floor in all directions, every now 

 and then turning and going straight back to the fly, and then starting 

 out again. If in the course of these wanderings it meets with 

 several of its fellows and rubs antennae with them, it then returns 

 to the fly, while its mates follow it in much excitement and a swarm 

 starts; but apparently the ''finder ant" has lost its sense of the 

 direction of the nest after having been carried through the air. 



But while this may apply to Monomorium destructor, it seems not 

 to be true for certain other ants. Thus, Brun found that Formica 

 rufa and several other species of ants have a remarkable sense of 

 direction which it is diflScult to confuse. This sense, according to 

 Brun, is complex and composed of perceptions which are chemical, 

 topographical, tactile, gravitational, and (as Santschi showed) a 

 perception of the direction of hght. They seem also to be able to 

 remember the "lay of the land," even after an interval of 3 weeks 

 between visits to a given region. It is possible that the flat floor 

 of the laboratory at Tortugas presented no topographical features of 

 sufficient definiteness to serve as guides to the ants, who became 

 lost, much as a good woodsman might be lost at sea. It is also 

 possible that different species of ants differ widely in their sense of 

 orientation, and that in Monomorium destructor this sense is some- 

 what poorly developed. 



VI. If the abdomen of an ant be shghtly notched or split with 

 a pair of fine dissecting scissors, so as to mark the ant, she does not 

 seem to be rendered abnormal in behavior by the operation, although 

 such ants are apt to die after a few hours, apparently through injury 

 to the tracheal system. If such an ant finds a dead fly it "inspects" 

 it in the normal fashion, and then starts oft" normally, but the other 

 ants pay no attention to it and are not excited if it rubs antennae 

 with them. At times, indeed, the normal ants may interfere with 

 the maimed ant, seizing it by the legs, so as to arrest its progress, 

 but generally they wholly ignore its presence. In any event, when 

 the marked "finder ant" has met several of her nest-mates and 

 rubbed antennae with them, she starts back in a straight course to 

 the fly, but none of the nest-mates follow it, and thus no swarm 

 occurs. In one experiment such a maimed "finder ant" repeated 

 this return journey eight times, each time after having rubbed 

 antennae with its nest-mates, but none of them followed her back 



