1907.] Wheeler, Fungus-growing A^its of North America. 679 



by the middle-sized "workers, and so get a ride home again. It is very 

 probable that they take a run out merely for air and exercise. The largest 

 class of what are called workers are, I believe, the directors and protectors 

 of the others. They are never seen out of the nest, excepting on particular 

 occasions, such as the migration of the ants, and when one of the working 

 columns or nests is attacked; they then come stalking up, and attack the 

 enemy with their strong jaws. Sometimes, when digging into the burrows, 

 one of these giants has unperceived climbed up my dress, and the first inti- 

 mation of his presence has been the burying of his jaws in my neck, from 

 which he would not fail to draw the blood." 



During his study of Aita in the province of Rio Grande de Sul, Brazil, 

 Fritz Aliiller appears to have reached independently the same conclusion 

 as Belt. A letter directed to Charles Darwin and published in 'Nature' 

 during 1874 contains the following remarks: "As to the leaf-cutting ants I 

 have always held the same view which is proposed by ]Mr. Belt, viz. that they 

 feed upon the fungus growing on the leaves they carry into their nests, 

 though I had not yet examined their stomachs. Now I find that the con- 

 tents of the stomach are colorless showing under the microscope some minute 

 globules, probably the spores of the fungus. I could find no trace of the 

 vegetable tissue which might have been derived from the leaves they gather; 

 and this I think, confirms Mr. Belt's hypothesis." 



Although observations on the habits of the Attii continued to be pub- 

 lished from time to time the suggestions of Belt and ^Miiller were either over- 

 looked or ignored for nearly twenty years. In his studies on Atta texana, 

 which, like those of Buckley, Lincecum and Townsend, were carried on at 

 Austin, Texas, McCook (lS79a, 18796, etc.) accurately described the formi- 

 caries and fungus gardens. He found the nests to consist of several chambers 

 or pockets, sometimes as much as 2 ft. 10 inches long, 12 inches broad and 

 8 inches high. The fungus gardens within these chambers are correctly 

 described as "masses of a very light, delicate leaf-paper wrought into what 

 may be properly called 'combs.' Some of the masses were in a single hemi- 

 sphere, filling the central part of the cave, others were arranged in columnar 

 masses 2^ inches high, in contact along the floor. Some of these columns 

 hung, like rude honeycomb or wasp nests from roots which interlaced the 

 chambers. The material Avas in some cases of a gray tint, in others of a 

 leaf-brown. It was all evidently composed of the fibre of leaves which 

 had been reduced to this form within the nest, proba])ly the joint action of 

 the mandibles and salivary glands. On examination they proved to be 

 composed of cells of various sizes, irregular in shape, but maintaining pretty 

 constantly the hexagon. Some of the cells Avere one-half inch in diameter, 

 many one-fourth inch, most of them one-eighth inch, and cjuite minute. 



