PSYCHOLOGY. 47 



numerous instances in which ants have appeared to exhibit reason- 

 ing powers. It is true that some of the examples given, such as ants 

 covering over tar, moisture, or unpleasant substances with earth, 

 or even with their Aphides, etc., to form a bridge as it would 

 appear, are not as conclusive as would be supposed, it being their 

 natural habit to cover up moisture or anything objectionable in 

 their nests. 



I have seen workers in my F. rufa observation-nest bringing 

 sticks, etc., from their hillock and casting them into the water- 

 trough as if to build a bridge, some individuals having even crossed 

 the water by this means ; but it may have only been a similar 

 case to the above. 



Ants which are subject to inundations have learnt how to protect 

 their colonies; Livingstone wrote of ants in Africa: "When all 

 the ant-horizon is submerged a foot deep, they manage to exist 

 by ascending to little houses built of black tenacious loam on 

 stalks of grass, and placed higher than the line of inundation." 

 When an ant colony has been washed out of its nest by sudden 

 heavy rain, or floods, the workers have been observed to collect 

 into a ball with the brood, etc., inside, those on the outside oc- 

 casionally changing places with the inner layers, and in this way 

 float down the stream, until a place of safety is reached. 



I once noticed a somewhat parallel case in my observation-nest 

 of Donisthorpea umbrata. Having filled the water-trough too full, 

 the superfluous water escaped under the glass cover and inundated 

 the chamber in which the brood and most of the ants were situated. 

 The workers immediately clustered round their larvae, enclosing 

 them completely, and remained in this position under the water, 

 until it had all been absorbed by the plaster walls and bottom of 

 the chamber. 



As space will not allow us to consider this subject at much 

 greater length, it is best to turn to, and discuss briefly, some of the 

 most striking psychological phenomena exhibited by ants. 



Ants know each other. 



Ants in a colony all know each other, but should a strange 

 ant be introduced, it is at once attacked, and killed or driven 

 out. Ants which have been separated for long periods readily 

 recognize each other again ; this has been demonstrated by 

 a number of myrmecologists, and I have myself repeatedly 

 found this to be the case with Formica rufa and other species. 

 It has been shown by bathing ants with the acid, or blood, 

 of strange species, with alcohol, and even only with water, that 

 they are no longer recognized by their friends, at least for a time 

 this proves that ants possess a special odour by which they are 

 known. It is not present in quite freshly hatched ants ; should, 



