300 A BOOK OF INSECTS 



stalks of the Aristida. In fact, after the seed has ripened 

 in the late summer they are said to clear away the dry 

 stalks in order to make way for a new crop. It is this 

 that justifies the reputation of Barbatus as a farmer. She 

 has not been seen — as far as the writer knows — sowing the 

 seeds, but she permits them to grow upon her formicary 

 bounds, and afterwards utilises the product." 



The most formidable foes to vegetation in Tropical 

 America are the large Saiiba or leaf-cutting ants of the 

 genus Atta. They dwell in extensive subterranean nests, 

 above which the excavated earth is piled into a mound 

 that may be thirty or forty feet in diameter. From these 

 strongholds the workers issue in gangs, and ascend the 

 trees. "Each one," writes Bates, "places itself on the 

 surface of a leaf, and cuts with its sharp scissor-like jaws 

 a nearly semi-circular incision on the upper side ; it then 

 takes the edge in its jaws, and by a sharp jerk detaches the 

 piece. Sometimes they let the leaf drop to the ground, 

 where a little heap accumulates, until carried off by 

 another relay of workers ; but, generally, each marches 

 off with the piece it has operated upon, and as all take 

 the same road to their colony, the path they follow be- 

 comes in a short time smooth and bare, looking like the 

 impression of a cart-wheel through the herbage." Along 

 these roads workers stream to and fro, and their energy 

 is such that they are capable of stripping a tree of its leaves 

 in a few hours. The use that these ants make of the 

 enormous bulk of material which they accumulate in their 

 habitations was for long a matter of speculation, but Belt 

 discovered that the original pieces of leaf were cut into 

 tiny fragments and piled up to form spongy-looking masses 

 within the chambers of the nest ; also that these masses 

 become clothed with a minute white fungus, upon which 

 the ants appeared to feed. It remained for the German 



