INSTINCTS OF HARVESTING ANTS 37 



The monotonous course of a harvester's Hfe is to 

 travel empty from the nest to the ant-field, select a 

 seed and return laden to the nest. I will later show 

 in the case of the geometrical spiders and certain 

 insects that when an instinctive routine has been 

 established, the creatures are in such bondage to that 

 routine that, in face of all obstacles, the course of 

 instinct must be fulfilled. Now the harvester, unlike 

 some other species, is not an absolute slave to its 

 routine. It can break the daily round of action in 

 order to suit altered conditions. For if the seed be 

 taken from a harvester on its return journey to the 

 nest, the ant, after vainly searching for its lost property, 

 will not behave like certain other insects would, and 

 pursue its fruitless journey empty-handed to the nest, 

 but will break its routine, turn about, and return for 

 another load. Also, if when travelling empty to the 

 field of harvest, it discovers a seed on the main track, 

 it is not impelled by instinctive routine to continue its 

 journey to the field, but will pick up the seed, face 

 about, and hurry off to the nest. Nevertheless, I 

 observed one foolish harvester, whose instinct seemed 

 a more powerful guiding force than its intelligence, 

 instead of turning back towards the nest after picking 

 up the seed from off the track, struggle on in its 

 instinctive routine and continue to carry the seed 

 towards the harvesting ground further and further 

 away from the nest. 



The refusal to submit to unswerving instinct is made 

 manifest in this way. Block the entrance to the 

 formicary and note the behaviour of the laden ants 

 when they arrive at the closed door. They immedi- 

 ately put things right. As soon as they arrive at the 



