1907.] Wheeler, Fungus-growing Ants of North America. 677 



a ball is made very much resembling coarse bees wax, and when dried is as 

 hard as dry putty. I judge the leaves by their decay produce a gentle heat, 

 or, at least, maintain a uniform temperature whereby the eggs are hatched. 

 Formerly it was suggested that these leaves constituted a store of food, but 

 such is not the case. Whether they feed upon vegetable or animal food I 

 cannot say." 



A new epoch in the study of the fungus growing ants was inaugurated by 

 Belt in 1S74 in his interesting volume, 'The Naturalist in Nicaragua.' He 

 was the first to surmise the use to which the leaves, etc., are put by the species 

 which he studied (probably A. cephalotes). As his work has become rather 

 rare, I quote the pertinent passages in full: "Notwithstanding that these 

 ants are so common throughout tropical America, and have excited the 

 attention of nearly every traveller, there still remains much doubt as to the 

 use to which the leaves are put. Some Naturalists have supposed that they 

 use them directly as food; others, that they roof their underground nests 

 with them. I believe the real use they make of them is as a manure, on 

 which grows a minute species of fungus, on which they feed; — that they are, 

 in reality, mushroom growers and eaters. This explanation is so extraor- 

 dinary and unexpected, that I may be permitted to enter somewhat at length 

 on the facts that led me to adopt it. "When I first began my warfare against 

 the ants that attacked my garden, I dug down deeply into some of their 

 nests. In our mining operations we also, on two occasions, carried our 

 excavations from below up through very large formicariums so that all 

 their underground workings were exposed to observation. I found their 

 nests below to consist of numerous rounded chambers, about as large as a 

 man's head, connected together by tunnelled passages leading from one 

 chamber to another. Notwithstanding that many columns of the ants 

 were continually carrying in the cut leaves, I could never find any quantity 

 of these in the burrows, and it was evident that they were used up in some 

 way immediately they were brought in. The chambers were always about 

 three parts filled with a speckled, brown, flocculent, spongy-looking mass 

 of a light and loosely connected substance. Throughout these masses were 

 numerous ants belonging to the smallest division of the workers, which do 

 not engage in leaf-carrying. Along with them were pupse and larvae, not 

 gathered together, but dispersed, apparently irregularly, throughout the 

 flocculent mass. This mass, which I have called the ant-food, proved, on 

 examination to be composed of minutely subdivided pieces of leaves, withered 

 to a brown color, and overgrown and lightly connected together by a minute 

 white fungus that ramified in every direction throughout it. I not only 

 found this fungus in every chamber I opened, but also in the chambers of 

 the nest of a distinct species that generally comes out only in the night-time, 



