ANTS— GENERAL INTELLIGENCE. 
139 
is Herr H. Kreplin, of Heidemiihl (Station Ducheroin), 
6 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 5 
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 4 thickheads ’ play the same role 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 trav* 1 
along the bank of the river until they arrive at a fiat 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 tkeir 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, but 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* 
