590 PSYCHICAL FACULTIES OF ANTS AND OTHER INSECTS. 



the jjlace he has found. Each of these then retraces the way and ]>oth 

 repeat the maneuver with other companions, etc. The recollection 

 that tiuit place is suitable for building a nest must reside in the brain 

 of the ant. The slave-making ants {Polyergus) will undertake robber 

 raids, led by a single worker, who, days and weeks before, has dis- 

 covered the way to the nests of Formica fusca. The ants often lose 

 their way, then stop and search for a long time until they again find 

 the topochemical trail, when they give to the others the right direction 

 for their farther journeying by sharply pushing them. The Polyer- 

 gus will take the pupa? of the Forinlca fuaca from the depths of the 

 nest and carry them otf to put into their own nests (often as far awa}' 

 as 40 meters or more). If the despoiled nest contains still more pup» 

 the robbers return on the same da}' or the following day; otherwise 

 they do not return. Only the memory, i. e., the recollection that there 

 were still many pupae in the despoiled nest can lead to the return 

 thither. 1 have followed up a great numl)or of such raids. 



While the species of Forinlea carefully and painstakingh' go back 

 over their topochemical trail, they know the immediate surroundings 

 of their nest so well that even shoveling away the ground does not 

 disturb them, and they find their way immediately. This is not by 

 perceiving the odor from a distance. Certain ants can recognize their 

 friends after the lapse of months. Among ants and bees there are 

 very complicated olfactory combinations and uiixtures, w hich Von But- 

 tel has quite justly distinguished as nest odor, colony (famil}') odor, 

 and individual odor. Among ants there is also a species odor, while 

 the queen odor does not appear to play such a part as it does among 

 bees. 



From these and many other facts we conclude that the social 

 Hymenoptera store up in their brains visual and olfactory (topochem- 

 ical) impressions, and combine then] to form perceptions or something 

 similar; that they associate these perceptions, even those of different 

 senses — especially those of sight, smell, and taste — so as to obtain 

 conceptions of space. 



These animals, by the frequent repetition of an act of traversing the 

 same wa}", etc., acquire a rapidity and a celerity in their instinctive 

 performances. Habits are formed by them with great rapidity. 

 Habit, however, implies secondary automatism and previous plastic 

 adaptation. Bees who have never flown away from the hive (although 

 they may be older than many others who have so flown) do not find 

 their way back at all, even if the hive is only a few meters distant, if 

 they can not see it directly, while other bees know the entire neigh- 

 borhood, often within a range of 6 or 7 kilometers. 



From the accordant observations of experts we therefore conclude 

 that among the social insects sensation, perception, association, deduct- 



