62 J. PEECY BAUMBERGER 



they are equally specialized. However, the origin of the habit 

 appears to be different, as will be seen later, therefore their fun- 

 gus gardening is best described at this point. Our knowledge of 

 these forms is specially due to the work of Bates ('63), Belt ('74), 

 Tanner ('92), and others. These ants excavate subterranean 

 nests composed of a series of chambers connected by a vertical 

 shaft usually ending in a crater. The fungus garden is built of 

 the comminuted fragments of leaves, cut from trees near the 

 nest, which have not passed through the digestive tract. The 

 little pellets thus formed are built up into the sponge-like mass 

 suspended from the ceiling or placed on the floors of the chambers. 

 Caterpillar droppings are quite commonly built into the comb, 

 which serves as a substratum for special kinds of fungi. A sum- 

 mary of all the literature on these ants, the tennites and the am- 

 brosia beetles, as well as some important contributions to the 

 ethology of American species, is given by Wheeler ('07), from 

 which I quote the following conclusions of MoUer: 



All the fungus-gardens of the Atta species I have investigated, are 

 pervaded with the same kind of mycelium, which produces the 'kohl- 

 rabi clusters' as long as the ants are cultivating the gardens. Under 

 the influence of the ants neither free aerial hyphae nor any fonn of fruit 

 are ever developed. The mycelium proliferates through the garden to 

 the complete exclusion of any alien fungus, and the fungus garden of a 

 nest represents in its entirety a pure culture of a single fungus. The 

 fungus has two different forms of conidia which arise in the garden 

 when it is removed from the influence of the ants. The hyphae have a 

 very pronounced tendency to produce swellings or diverticula, which 

 show several more or less peculiar and clearly differentiated variations. 

 One of these, which has presumably reached its present form through 

 the influence of cultivation and selection on the part of the ants, is 

 represented by the 'kohlrabi heads.' Under artificial conditions the 

 'kohlrabi clusters' and 'heads' disappear and the fungus becomes a 

 mass of bead-like conidia. 



Sampaio ('94), von Ihering ('98), Goeldi ('05), and Huber 

 ('05) have shown how the new fungus colony is started after the 

 marriage flight. The queen dealates itself, digs a small subter- 

 ranean burrow which it closes and then starts the new colony by 

 spitting out a pellet of fungous hyphae which had been carried 

 in the buccal pocket and depositing eggs upon it. The fungus 



