68 Riley Presidential Address. 



nearly to the apex of the sclerite as in the case of the fertile female in Apis. 

 In Bombus the structure is almost identically the same as in Melipona. 



* NOTE 5. Ant Economy. 



Considering the large number of species of ants, a book would be re 

 quired to treat of them in detail, and volumes have been written. In 

 this note I shall only treat of a few of the better known, to supplement the 

 mere summary in the body of the address. The most interesting of our 

 North American species which I have had an opportunity of studying are 

 the mound-building species of the East, the leaf-cutting species of Florida 

 and Texas, and the honey ants of Colorado. With the aid of Mr. Th. 

 Pergande, who has been assiduous in his studies of the family, and is per 

 haps our best-informed myrmecologist, I have brought together a number 

 of notes on the habits of our North American species of Carpenter Ants 

 and others ; but they are excluded as the least important in connection 

 with the text, and with a view of duly limiting the pages. 



MOUND-BUILDING ANTS. In this category may be classed by far the 

 larger number of our better-known ants. The term is, however, particularly 

 applicable to the species of the genus Formica. These ants are very much 

 more active and industrious and typical of the family, than are the carpen 

 ter ants. Our own species inhabit, by preference, pine woods. They are 

 pugnacious and valiant, and whenever their mound is disturbed, however 

 slightly, will speedily cover the whole surface in one surging mass, spread 

 ing over the mound and attacking in their fury any living creature within 

 reach. They are in fact so fierce and fearless that even man does 

 well to avoid their mounds ; for the bite is quite severe, and when multi 

 plied indefinitely is unbearable. 



The Fallow ant (Formica exsectoides Forel), one of our best known species 

 and a close ally of F. exsecta of Europe, builds large mounds of earth, more 

 or less mixed with other materials, especially small sticks and dried leaves 

 of pine. These will measure all the way from two to eight feet in diameter 

 at the base, and may be from one to three feet high. They are more or less 

 regular and conical, full of galleries, with larger or smaller chambers which 

 communicate with a general system of subterranean cells or cavities, which 

 are used as store-rooms, nurseries for the young, parlors for the queens, and 

 other purposes. The purpose of the superstructure hi most mound- build 

 ing ants appears to be for aeration, for the more rapid development 

 of the larvae, and, apparantly, to facilitate social intercouse between the 

 individuals when not engaged in actual work. Except for the extrane 

 ous matter which gives it firmness, all the material of the mound is brought 

 up from beneath the surface, and the inhabitants are incessantly at work, 

 night and day, in constructing, altering and repairing. Very large 

 colonies are often connected by secondary hills. I once had a good oppor 

 tunity of studying these mounds around Ithaca, N. Y., and Dr. H. C. Mc- 

 Cook has published a most interesting and detailed account of his observa 

 tions upon this ant in the Trans. American Entomological Society for 1877, 

 Vol. VI, page 253, and also in The American Naturaliat for July, 1878, Vol. 

 XII, pp. 431-445. It is particularly common in the Alleganies. There are 

 three forms of workers, viz, major, minor and dwarf. His interesting ob 

 servations will well repay reading. 



It is in these mound-building ants that we find the true economy of the 

 division of labor. While large numbers are ceaselessly building and min 

 ing, so as to keep the formicary in good condition, repairing or increasing 

 its size, so as to accommodate the growing numbers, others are busily engaged 

 in scouring the surrounding country for food, both for themselves, for the 

 multitude of those who stay at home, and for the young. In these expedi 

 tions they never hesitate to attack any other insect that may be in their 

 way, no matter how much larger than themselves, and what they lack in 

 power individually they make up in numbers. Still others again are run- 



