498 ants' nests. 



7.— compound nest.s. 



Ill the Communications of the Swiss Entomoh)gical Society, Vol. Ill, 

 part 3, 1860 (Observations on the habits of l^olenopsin fuf/ax), I first 

 calh'd attention to the fact that two hostiki species of ants can live in 

 nests which are regularly intercalated. In my "Fourmis de la Suisse" 

 (1874), I showed that such relatnuis occur very freciuently and more or 

 less accidentally among many species of ants, especially under stones 

 tliat are well adapted to nests and greatly in demand; wlide, in tSolen- 

 opsis fugax Latr., "double nests" form a very ordinary, in fact, the 

 most ordinary, occurrence, at least in our meadows. Wasmann (The 

 Conii)Ound ISests and Mixed Colonies of Ants, Miinster i, AV., 1891, 

 Aschendorff's) has corroborated and supi)lemeiited my observations on 

 this subject. Instead of the name "double nests," used by me, he has 

 introduced the more correct expression "compound nests" (to be trans- 

 lated into French by "nids composes"). In fact, these nests are not 

 untrequently threefold, and even fourfold — that is to say, the nests of 

 from three to four difi'erent and hostile species of ants are built into 

 each other, without, however, having any open communication with 

 each other. If the partitions are destroyed, war ensues immediately. 

 The worker of Holenopfih fuga.r is a puny, yellowish ant, hardly 2 milli- 

 meters in length, but the females grow to an imposing size, and look 

 like giants by the side of the workers. This species is in the habit of 

 digging its nests in the thick walls of the nests of the ants of the 

 larger species, and in such a manner that,wheiever there is room, large 

 halls are constructed (fig. G, S), in which the females and the males are 

 comfortably lodged with their large pupa? and larva', while small pas- 

 sages connect these halls. Extremely small passages, not visible in the 

 figure, afford the workers exclusively admission to the chambers of the 

 host ant (fig. (J, Foi). According to my observations and those of 

 "Wasmann, Solenopsis fugax lives like a thief and little robber, at the 

 expense of its involuntary host. The little workers make their way 

 through extremely small passages to the pupa and larva heaps of the 

 large ants and devour them from underneath without being seen, thanks 

 to their small size. They also devour openly the forage supplies, as 

 well as the dead and sick individuals, of the larger species (mostly 

 Formica fusca L., but also Formica riifa, F. pratensis, F. f>anf/uinea, 

 Poli/ergns rufcsceits, Lasius niger, etc.). 



Fig. () reijresents a fragment of a. double uest of Formiva fusca and 

 SoJeuopsis fugax from the Zurich Mountain. By means of dissolved 

 shellac, which I jwured upon the nest in fine weather, and then allowed 

 to dry, I succeeded in making it firm enough to be able to take it out 

 without injuring it. The fine-grained, polished interior walls of the 

 i^olcno2)sis cavities are seen, in contrast to the coarse-grained and more 

 spaci(ms Formica chambers. As the ants take up the moist earth with 

 their mandibles in the form of small lumps, and then work it into shape 

 with their jaws and forelegs, in order to construct their masonry with 



