ants' nests. 359 



Formica rufa, i. sp., of the fir woods, uses chiefly fir leaves 

 Formica pratensis of the meadows builds flatter mounds and uses 

 more pieces of wood and blades of grass, pieces of dry branches, 

 etc. ; For7tiica exsecta uses more particles of dry leaves, etc. ; 

 Formica sanguinea^ Latr., builds mounds composed of the above- 

 mentioned materials and earth ; its work is partly that of a 

 carpenter and partly masonry ; the latter, however, which is 

 executed by the "slaves" (Formica fusca), usually prevails. 



It is impossible for us to describe everything, and we refer our 

 readers to Ruber's admirable description of the way in which the 

 forest ants and the earthen-mound ants build their nests. It may 

 well be said that almost every species — either in earthen structures, 

 in wood nests, or in combined structures — has its peculiarities 

 with regard to the quality of the material, the fineness of the grain, 

 the shape and arrangement of the mound and the labyrinth, the 

 comparative thickness of the walls, the size of the chambers, etc., 

 so that the species may frequently be known by the structure. 



Still the ants often rob one another's nests, and this frequently 

 renders it difiicult to recognise the architect. 



There are species, it is true, whose architecture can hardly be 

 distinguished, as, for instance, the little species of Myrmica. 



5. — Pasteboard Nests and Spun Nests. 



I have already, in the Mittheilunge?i of the Swiss Entomologi- 

 cal Society^ Vol. VIII. , part 6, 1891, given some information with 

 regard to the singular nests which are now to occupy our attention. 

 A well-known European species, Lasius fuliginosus, Latr., builds 

 peculiar pasteboard nests, which Huber erroneously thought to be 

 excavated in wood, while Meinert, Mayr, and others, including 

 myself, have demonstrated their true nature beyond a doubt. 

 They are composed of the finest particles of wood dust or of earth 

 and small stones, which, by means of a viscous substance secreted 

 by the ants, are worked up into so strong a pasteboard (see Forel, 

 Four77iis de la Suisse, pp. 181 — 187) that the partitions between 

 the excavations are extremely thin (as thin as visiting cards). 

 These nests are mostly found in hollow trees. That they are not 

 excavated, but are composed of pasteboard, I have clearly shown 

 by microscopic cuts. Meinert first called attention to the fact that 



