352 ants' nests. 



myself have watched innumerable times. It is, however, an 

 unsolved problem whether really, as Huber thought, water alone 

 always suffices as cement for the earth or whether it is not in some 

 cases mixed with a secretion of the glands of the ants. The 

 great firmness of certain structures — for instance, those of Lasius 

 flavus — gives some probability to the latter supposition, particu- 

 larly when we consider the fragile character of the structures of 

 other kinds of ants. 



Earth nests may be divided into three classes : — 



(a) Nests which are ejitirely excavated. — In this case passages 

 and chambers are simply excavated in the ground, without the 

 particles of earth w^hich are dug out being worked up into an arti- 

 ficial upper structure ; they are merely thrown away. There are 

 many kinds of ants which mine only in this way, as, for example, 

 Ponera contracta, Ltr.. Mynnecocystus, all the Dorylides^ Aphceno- 

 gaster subterranea, Ltr., and, in general, most of the blind and 

 half-blind species. Besides these, many other species do it 

 occasionally, such as For??iica fusca, L., Formica rufibarbis, F., 

 Tetramorium ccespitwn, L., species of Mynnica^ etc. 



One variety of the mined nests consists of those in which the 

 ants heap up the excavated earth in banks around the openings of 

 the nest, so that crater-shaped openings are the result. This 

 occurs most frequently in sandy soil. These banks are not 

 genuine upper structures, although they often resemble them 

 closely. We find them in the case of Messor structor, Messor bar- 

 barus^ species oi Fheidok, Acantholepis frauenfeldi, Pogotwmyrmex^ 

 etc. A peculiar variety of this class is formed by the crescent- 

 shaped mounds of Messor arenarius, Fab., first noticed by me in 

 the South Tunis desert near Cabes, which consist of coarse but 

 very perishable globes of sand. At certain times the apertures of 

 the Messor nests are, in addition, surrounded by mounds com- 

 posed of the hulls of the seeds which have been gathered, which 

 hulls have been thrown out of the nests. The little Cardiocondyla 

 elegans^ Em., and stambuloffii, Forel, make small nests in the sand 

 on the seashore. 



The subterranean structures of some kinds of ants are, in 

 certain cases, extremely interesting. Certain species dig passages 

 which go down very deep and branch off laterally, forming subter- 



