BIOLOGIC RELATIONS BETWEEN PLANTS AND ANTS. 419 



roads which extend to their nests. These are trodden night and day 

 by thousands of workers, and soon become smooth and bare, resembling 

 the tracks of a cart wheel passing through the herbage. The severed 

 grass is thrown out on the sides of the road. 



The voracity of the (Ecodomas is such that, in the countries they 

 infest, it is almost impossible to naturalize certain trees, such as citron 

 and orange trees. Lund states that, when on a voyage of exploration 

 in Brazil, he was very much astonished to hear, during calm weather, 

 a noise like rain, caused by leaves falling to the ground. He was 

 standing under a laurel tree 12 feet high, having coriaceous leaves 

 which were detached, although having their natural green color, thus 

 having no resemblance to diseased leaves. He saw then that each 

 petiole had upon it an ant that was trying to cut it off. Each leaf 

 severed and tbrown to the ground was seized by the (Ecodornas, who 

 immediately cut it up and carried the fragments to their nest. In less 

 than an hour the tree was stripped and resembled a gigantic broom. 



Did Lund meet with some other species of (Ecodoma than the (Eco- 

 doma cephalotesf If not, the ants know how to modify their method of 

 harvesting, sometimes cutting round pieces out of leaves still attached 

 by their petioles, sometimes cutting the petiole directly through. The 

 leaves are taken into the ant-hill in a condition neither too dry nor too 

 moist. If they are too moist they are dried uear the entrance, and, if 

 rain continues, finally abandoned. If the weather is too dry the leaves 

 are gathered only at night. By the opening or closing of certain gal- 

 leries a suitable ventilation is also kept up. In order to facilitate this 

 their hills are never located in the interior of forests, where the air does 

 not circulate well, but on the edge of clearings. 



Of what use can these harvested leaves be to the ants! Various 

 hypotheses have been proposed on this subject. The most probable 

 is that of Belt, who supposes that they are used to make a real compost 

 on which small mushrooms grow, that serve the ants for food. If, 

 indeed, we open an anthill we do not see there any leaves, but find 

 in many communicating chambers a brown flocculent matter, in the 

 midst of which are found ants much smaller than the leaf-cutting 

 workers, together with larva? and pupse. 



These little ants sometimes go out of the nest and follow the paths 

 traversed by the workers; but they never carry anything, and are even 

 themselves carried back again by the workers, seated upon the round 

 piecesof leaves transported by the latter. There is apparently assigned 

 to them the task of reducing to small fragments the leaves brought 

 into the nest, and they work only in the depths of the colony. 



It is not only leaves that are used by the ants to make their compost, 

 but certain flowers belonging to plants the leaves of which they do not 

 attack, and the inner white rind of oranges. Like the harvester ants of 

 our own country, they sometimes carry in by mistake useless materials, 

 but they soon discover this and drag them outside. 



