470 



J. C. BRANNER GEOLOGIC WORK OF ANTS 



found. The largest ones measured were on the upper drainage of Kio 

 Utinga; several of these were found to be 5 meters high and 16 and 17 

 meters in diameter at the base, and each contained^ therefore, about 340 

 cubic meters of earth. There were no other mounds closer to these than 

 10 or 15 meters. 



M. Gounelle, a French entomologist, has calculated from a photograph 

 the size of some of the Bahia mounds. Following is a translation of a 

 part of his article. The mounds mentioned by him are near Condeuba, 

 which is in the southern part of the State :^^ 



"A photograph shown to the Society makes it possible for one to appreciate 

 the enormous amount of work done by certain ants, and to measure fairly well 

 the volume of the materials moved by them in digging their galleries. This 

 photograph, taken in the vicinity of the little city of Condeuba, in the south- 

 ern part of the State of Bahia, shows a clearing in which appear five conical 

 nests of an ant, probably Oecodoma cephalotes Latreille.-^ The five cones 

 have about the same dimensions. One notes in the foreground that the scale 

 is one centimetre to the metre, as is readily seen by comparison with the man 

 standing on top of the mound. Its diameter is 16 metres and its height is 4.5 

 metres, which by a simple calculation gives 301 cubic metres for its volume 

 and 1,500 cubic metres for the total volume of the five mounds. The clearing 

 has a surface of about one hectare, so that the earth of the five mounds, if 

 spread evenly all over it, would have a thickness of 15 centimetres. . . . 

 It should be added that the building of ant-hills of this size within a limited 

 area is not an isolated case. The traveller in these regions meets with them 

 everywhere, and that, too, over an enormous extent of country." 



The reader should be reminded just here that this sort of thing is not 

 to be seen in all parts of the country, by any manner of means. So far 

 as my own observations go, ant mounds are unusually large and unusually 

 abundant in this particular part of Brazil. 



Age of the mounds. — The amount of work done by these ants in a re- 

 gion where they seem to be favorably located is fairly well shown in the 

 preceding table. Trustworthy data for calculating the time required to 

 build a mound of a given size or to do any given amount of work is lack- 

 ing. ^Necessarily the time must vary with the size of the colonies, other 

 things being equal. The colonies, however, appear to have their ups and 

 downs, for while some of them increase in numbers and continue to add 

 to the mounds for long periods, others appear to be less active, while 

 still others disappear, whether by migrating or through the death or cap- 

 tivity of the members is not certainly known at present. It is interest- 

 ing to note that the Brazilians generally regard the size of the ant-hill as 



-'' E. Gounelle : Transport de terres effectue par des fourmis au Bresil. Annales de la 

 Societe Entomologique de Prance, 7me ser., no. 6, pp. 332-333. Paris, 1896. 

 29 This is tlie name of the so-called saiiba. J. C. B. 



