GEOLOGIC WORK OP ANTS — BRANNER. 313 



ering only the largest and oldest ones made by a single species, and 

 found in various different localities, it is noteworthy that there is a 

 great difference in the sizes of the largest of them. Just what deter- 

 mines this variation I can not say positively, but the influences 

 referred to above — that is, rainfall, character of soil, and vegetation — 

 naturally suggest themselves as possible influences. 



Nowhere do I remember to have seen more or larger ant hills than 

 along Rio Utinga, in the diamond regions of the interior of the State 

 of Bahia. From the town Riachao, down the river to the village of 

 Pegas, the examples are big and abundant. In a few places they are 

 so close together that, big and little, they appear to cover half of the 

 ground. My notes, written on the spot, say ''more than half of the 

 ground." Such places, however, are exceptional. The distribution 

 is always more or less irregular — bunched apparently on account of 

 characteristics of soil or drainage, or for some other reason that does 

 not appear. In some areas of from 10 to 20 acres the ant hills 

 occupy from a fifth to a third of the ground, while over larger tracts 

 they take up from one-eighth to a seventh of the ground. In height 

 the mounds are often as much as 5 meters high, with bases 15 or 16 

 meters in diameter. In the forests these mounds are generally over- 

 grown with young trees. On maivy of the big mounds I have seen 

 trees more than 30 centimeters in diameter. At the village of 

 Antonio Jose the people have planted pineapples upon the mounds. 



At fazenda Bello Horizonte, about 18 kilometers north of the village 

 of Pegas, the ant lulls are so large and stand so thickly upon the 

 ground that they form one of the most striking illustrations I have 

 ever seen of the work of these insects. An area of some 30 acres or 

 more is there covered with mounds resembling haycocks. They 

 probably average 2 meters in height and a diameter of 4 or 5 meters 

 at the base. 



At a place called Ponte Nova, on Rio Utinga, 8 kilometers north 

 of the village of Pegas, the ant lulls are a remarkable feature of the 

 landscape. To the east and northeast of the Protestant college the 

 mounds cover the old fields. One of the accompanying photographs 

 (fig. 2, pi. 1) and text figure 1 were made in this region. 



Six kilometers north of the station one was found by measurement 

 to be 1.8 meters high and 4.5+ meters wide at the base. This 

 mound was not regarded by the people of the locality as any tiling 

 unusual. 



To the east of Serrinha several mounds were observed with a height 

 of 3 meters and a diameter at the base of 10 meters. The^e mounds, 

 therefore, contain each 78.5 cubic meters of earth. 



Along the western half of the Bahia and Minas Railway, that starts 

 from the coast near Caravellas, in the southern part of the State of 



