738 Bulletin American Museum of Natural History. [Vol. XXIII, 



These dilatations, two of which are indicated in the diagram, must have 

 represented the chambers of the incipient nest and one of them was undoubt- 

 edly the original cell excavated by the mother cjueen of the colony. 



In collecting the vegetable substances to serve as a substratum on which 

 to grow their fungus, the workers of Afta iexanci seem to show no evidences- 

 of discrimination, further than that a colony usually concentrates its atten- 

 tion on one kind of material on each of its forays. I have seen workers of 

 the same colony at different times cutting and carrying home the leaves 

 of plants belonging to the most diverse natural orders. They seem indeed 

 to prefer plants with small or rather narrow^ leaves, but the texture of the 

 leaves is apparently a matter of little importance, for the ants may be seen 

 defoliating soft herbs like the sheep sorrel (Rumex acetosella) or the clover, 

 and anon attacking the tough leathery foliage of the live oak (Quercus 

 virginiaua). But even hard berries like those of the juniper are collected 

 and embedded entire in the gardens. Once I saw a colony carrying away 

 the cracked grains of maize from a hominy mill, and on another occasion 

 the same colony was assiduously gathering large caterpillar droppings that 

 had rained down from a plane tree near the nest. These ants occasion- 

 ally enter gardens and defoliate rose-bushes or other ornamental shrubs 

 or destroy tender vegetables, but their inability to concentrate their attacks, 

 for several consecutive days on particular species of plants, and the some- 

 what smaller size of their colonies than those of the tropical Atfce, make 

 them much less dangerous economically than might be supposed. 



Like many other Texan ants, Atta texana is more sensitive to the heat 

 than to the sunlight. I infer this from the fact that during the w^inter and 

 cool autumn and spring months it forages at all times of the day but during 

 the hot summer months carries on its excavations and goes abroad only 

 during the cool night hours. The sensitiveness of these ants to heat and to 

 the humidity of the air is also shown by the fact that they carefully close 

 their nest craters with earth, leaves, or sticks during hot, dry spells. This 

 seems to be an adaptation for preventing the escape of the moisture from the 

 nest through the large ventilating galleries and the consequent injury to the 

 proliferating mycelia in the gardens. While opening the nest chambers 

 of this and other species of Attii I have often seen the delicate fungi wither 

 up within a few moments after exposure to the dry air. 



I have not observed in Atta texana the method of comminuting the leaf- 

 clippings but there can be little doubt that it is very much like that em- 

 ployed by A. cephalotes and Acromijrmex discigera as described by Tanner 

 and Moeller. The macroscopic structure of the gardens (Figs. 14 and 15) has 

 been correctly described by McCook (ajite, p. 679). Their microscopic 

 structure resembles very closely that of the Acromi/rmex studied by Moeller. 



