ANTS GENERAL INTELLIGENCE. 139 



is Herr H. Kreplin, of Heidemiibl (Station Ducheroin), 

 4 who lived for nearly twenty years in South America as 

 an engineer, and had often the opportunity of seeing the 

 driver ants in the forests there.' He writes to Biichner, 

 under date May 10, 1876, as follows : 



On both sides of the train, at about 10 mm. distance from 

 each other, stronger ants are to be seen, distinguishable from 

 the others by their foxy colour and very thick heads with 

 gigantic mandibles. These ' thickheads ' play the same rdle in 

 the ant-state for which they are cast in cultured communities. 

 They look after the order of the march, and allow none to turn 

 either to the right or left. The least confusion in the regularity 

 of the march makes them turn round and put things straight 

 again. While the procession of the brown workers streams 

 on unceasingly with a swarming motion, the ' officers,' as the 

 natives call these thickheads, run constantly backwards and 

 forwards, ready to take the command on meeting any difficulty. 

 The crossing of streams by these creatures is the most interest- 

 ing point. If the watercourse be narrow, the thickheads soon 

 find trees, the branches of which meet on the bank on either 

 side, and after a short halt the column set themselves in motion 

 over these bridges, rearranging themselves in the narrow train 

 with marvellous quickness on reaching the further side. But 

 if no natural bridge be available for the passage, they travt 1 

 along the bank of the river until they arrive at a flat sandy 

 shore. Each ant now seizes a bit of dry wood, pulls it into the 

 water, and mounts thereupon. The hinder rows push the front 

 ones even further out, holding on to the wood with their feet 

 and to their comrades with their jaws. In a short time the 

 water is covered with ants, and when the raft has grown too 

 large to be held together by the small creatures' strength, a part 

 breaks itself off and begins the journey across, while the ants 

 left on the bank busily pull their bits of wood into the water, 

 and work at enlarging the ferry-boat until it again breaks. 

 This is repeated as long as an .ant remains on shore. I had 

 often heard described this method of crossing rivers, b\it in the 

 year 1859 I had the opportunity of seeing it for myself. 



It is remarkable that the military or driving ants of 

 Africa exhibit precisely similar devices for the bridging of 

 streams, namely, by forming a chain of individuals over 

 which the others pass. By means of similar chains they 

 also let themselves down from trees. It must be observed, 



