INTEODUCTORY 451 



The western halves of Oklahoma, Kansas, and Nebraska and the east- 

 ern portion of Colorado are inhabited by monnd-building prairie ants 

 that are sufficiently abundant and sufficiently pugnacious to have attracted 

 the attention of farmers and entomologists, if not of geologists.^ 



In the Western States generally ants are more abundant than they 

 are in the East, but a writer on the ant-hills of southwestern Wisconsin 

 says that in that part of the country he knows of at least a hundred so- 

 called ant-hills within a radius of 5 miles, and he appears to regard this 

 number as quite striking. Their mounds, he says, are as much as 75 

 centimeters in diameter and 40 centimeters in height.* These cases are 

 mentioned simply for the purpose of contrasting the size and number of 

 ant-hills in a region that seems to be regarded as pretty thickly inhabited 

 with some of the typical localities in the tropical portions of South 

 America. 



Furthermore, in the tropical parts of America ants are not the simple 

 and easily ignored insects with which we are acquainted in the temperate 

 zones of the earth. Save in the cities, they are almost omnipresent. To 

 the housekeeper they are not only never-sleeping pests, but they are bold 

 and defiant robbers or sneak thieves, as circumstances require, and they 

 can not be ignored. To the planters they are veritable plagues — they 

 destroy the growing crops as completely as if they had been burned over. 

 They do not wipe out a field of grain in a few hours as completely as do 

 the locust swarms of Argentina, and then disappear, but they stay with 

 their work right alongside of the crops, and with time they destroy them 

 no less certainly. Unlike the locusts, they do not come and depart, but 

 they stay right in one circumscribed area all their lives. Farinha de 

 mandioca, the meal prepared from the cassava plant, or grain of a size 

 small enough for them to carry, require to be guarded with constant care. 

 I have known bagfuls of farinha de mandioca to be carried away by 

 them. In short, the inhabitants have to be constantly on their guard 

 against the ants, both indoors and out of doors, to say nothing of the mere 

 inconvenience of their presence. !N'or can their importance be regarded 

 as whimsical in any sense; indeed, I am convinced that they are social, 

 and even national, factors that are not to be ignored. 



Nothing in the way of a biologic or systematic study of tropical ants is 

 attempted in the present paper. However valuable such a study might 

 be, it is the number of individuals, rather than the number of species, 

 that concerns the geologist, though it is recognized, of course, that some 



3 T. J. Headlee and George A. Dean : The mound-building prairie ant (Pogonomyrmex 

 occidentalis Cresson). Bull. 154, Kansas Agricultural Experimental Station. Manhat- 

 tan, 1908. 



* Hermann Muckermann : Psyche, vol. ix, pp. 35o-360. Boston, 1902. 



