684 THE POPULAR SCIENCE MONTHLY. 



A most curious fact in ant-life lias been observed by the emi- 

 nent French chemist, M. Berthelot, who is also a zealous ento- 

 mologist. He noticed in a little wood a nourishing city of ants 

 which for several successive years went on enlarging its struct- 

 ures and laying out roads in every direction. At last, without 

 any manifest cause, it began gradually to decay. It had not been 

 afflicted by wars, nor by scarcity of provisions ; yet the number 

 of its inmates seemed to diminish, their energy and activity faded, 

 and their domes and galleries, no longer kept in repair, took a 

 desolate and ruinous aspect. On the other hand, a colony which 

 the old ant-hill had formerly sent out to a considerable distance 

 was becoming the leading city of the district. "What might be 

 the cause of this decay of the mother-city is, of course, very 

 doubtful. Perhaps its inmates had had an attack of what is now 

 called " national conscience." Perhaps in a fit of " magnificent self- 

 abnegation " a modern synonym for suicide they had decided 

 that it was selfish to look after their own interests, and decreed 

 that such ought to be allowed to perish. Or, it might be merely 

 an instance of the fact that not merely individuals, but communi- 

 ties, races, and species are mortal the loss of vitality having its 

 wider analogue in the decay of the tribal instinct. 



I have formerly witnessed a very similar case among rooks. 

 A huge ash tree, flourishing in the court of a suburban mansion, 

 and known familiarly as the " crow tree," had been, for a term 

 of years going beyond my remembrance, tenanted by a com- 

 munity of rooks to the extent of perhaps twenty-five to thirty 

 nests each season. At last there set in a gradual falling off. 

 From year to year the number of inhabited nests decreased, and 

 those which were unoccupied fell to ruin or were carried off as 

 building materials. When I last had occasion to pass through 

 the town, only two nests remained in the old " crow tree." 



All this time a new rookery had been founded in a park at 

 about a mile outside the town, and thither the former denizens of 

 the tree emigrated. This colony is now much more populous than 

 the old settlement had ever been. 



The cause of the " decline and fall " is as mysterious as that of 

 M. Berthelot's ant-hill. The birds had not been in any way mo- 

 lested ; their ranks had evidently not been thinned by disease, or 

 the new rookery could not have increased so rapidly. 



But, whatever might be the causes in these two instances, we 

 see here another feature in common between human nations and 

 the nations of the lower animals. 



It has been observed that even common misfortunes will not 

 compel animals of one and the same species, but belonging to dif- 

 ferent nationalities, to unite. This fact has come under the notice 

 of elephant-hunters. It has sometimes happened that two distinct 



