ANTS. 





the only food of tin- species of Atta." These clusters are made up of 

 the "heads of kohlrabi which are small terminal dilatations of the hyphae 

 of a spherical or oval iorm." Mueller confirmed licit'.-. ohservation> 

 on the solicitude of the ants for their gardens, and showed that these 

 insects in artificial nest> will completely rebuild these structures within 

 twelve hours after they have been disintegrated or scattered. He saw 

 the ants eating the fungus and was able to satisfy himself that the 

 different species of Atta will eat the kohlrabi from one another's colo- 

 nies, but not that of Apterostigina or Cyphomyrmex. Kelt supposed 

 that the smallest workers, or minims comminute the leaves and build 

 up the fungus gardens. According to Moeller, however, this is the 



office of the mediae, as the leaves are too thick 

 to be manipulated by the smallest workers. The 

 latter have another function, namely, that of 

 weeding the garden and keeping down the growth 

 of spores belonging to alien fungi. Moeller 

 emphasizes the remarkable fact that the gardens 

 are pure cultures although the hairy, rough- 

 bodied workers must be continually bringing into 

 the nests all sorts of spores and bacteria. It is 

 probable, also, that the minims are instrumental 

 in producing the " kohlrabi heads," as these are 

 not developed when the mycelium is grown in 

 artificial culture media apart from the influence 

 of the ants. He summarizes the results of this 

 portion of his studies in the following words : 

 " All the fungus-gardens of the Atta species I 

 have investigated, are pervaded with the same 

 kind of mycelium, which produces the ' kohlrabi 

 clusters ' as long as the ants are cultivating the 

 gardens. Under the influence of the ants neither 

 free aerial hyphae nor any form 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 differ- 

 entiated 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.' ' 



, . 

 - 



FIG. 194. Diagram 

 of nest of Trachymyr- 

 mex turrife.r with five 

 chambers. The right 

 half of the figure is a 

 continuation of the 

 lower portion of the 

 left half. (Original.) 



