A most curious fact in ant-life has been observed by the eminent French chemist, M. Berthelot, who is also a zealous entomologist. He noticed in a little wood a nourishing city of ants which for several successive years went on enlarging its structures 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 communities, 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 community 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 molested; 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 different nationalities, to unite. This fact has come under the notice of elephant-hunters. It has sometimes happened that two distinct