ants' nests. 487 



among" the living ants). That the part played by the Colobopsis "sol 

 diers"' is that of a living- stopper is further proved by the fact that there 

 are comparatively few of them, and that iu contrast to the workers they 

 hardly ever go out. Fig. 19 represents a " soldier," still more magnifled, 

 standing at the door of egress. 



Those species of Camponotus which live in a similar way, such as 

 Camponotus marginatus Latr., display the beginning of a similar 

 rounded surface on the front part of the head, and always have a large- 

 headed sentry at the door. 



Ltptothorax acervonim F. cuts small, very simjile nests, sjiread out 

 flat, with few chambers in the outer layer (the cork layer) of the bark 

 of the tree. Fig. 5 represents such a nest two-thirds of the natural size 

 in the bark of a lir. 



4.— COMBINED STRUCTURES. 



The structures heretofore described are combined in a variety of 

 ways. 



For instance, the hollow stalk of a large Arcangelica is idled from 

 top to bottom by LasiKs nhjcr with small earthen chambers and occu- 

 pied by them. Decayed trunks of trees are made use of by cuts which 

 elsewhere build iu the ground, excavated, and worked up into nests by 

 Lasius niyer, Lasius favKS, Formica fusca, ]\ryrmiv(( Iceviuodis, etc. 

 Here wood dust and earth are used as mortar in the construction of 

 chand)ers and galleries. Formica rufa L. excavates the softer portions 

 of the wood in half decayed trunks of trees and builds in them laby- 

 rinths which form a part of its nests. 



Lasius brunneus Latr. lives habitually in half-rotten trunks of trees 

 and beams, after excavating the moist, decayed wood. It also lives in 

 decayed woodwork in our houses, as do likewise frequently Liisius 

 nm brat us ISTgl. 



The architecture of the grouj) of forest ants, Formica rufa L., praf en- 

 sis De Geer, trnncicola Nyl., exsecta Ngl., and pressilahris Nyl., as 

 well as of their North American relatives, F. exsectoidcs Forel, iuleyra 

 Nyl., obscuripes Forel, etc., is, however, more imposing and more 

 interesting. 



These ants nune the ground, but cover their nests with dry vegetable 

 matter of the most varied kinds — pine and fir cones, dry leaves and 

 pieces of wood, snail shells, little balls of rosin; blades of grass, in a 

 word, with every kind of round and cylindrical materials. With these 

 they build the well-known immense mounds, with their singular frame- 

 work and the indescribable interior labyrinth, the most thoroughly 

 perforated part of which is in the middle, at about the level of the 

 ground. Earth serves partially as cement. The openings of the nest 

 are carefully closed with small pieces of wood at night or when it is 

 raining. They are opened by the workers in the morning and generally 

 iu warnj, fine weather. 



