412 Bulletin American Museum of Natural History. [Vol. XXII^ 



fact that the moss attracts and retains water, so that these portions 

 become rather moist and therefore unsuitable as a dwelling for the 

 insects. 



"ii. It follows as a general conclusion from paragraphs 5-10 

 that there must be between the Polytrichum and the ants a severe 

 struggle in which the moss is always victorious. 



"12. Sphagnum often gains a foothold on the hill before the 

 Polytrichum. has completely overgrown the summit, or umbilicus. 

 Sphagnum, generally speaking, displaces Polytrichum. This is cer- 

 tainly the case wherever the Polytrichum hills have not been destroyed. 

 From this follows: 



"13. The Polytrichmn-hvim.m.ock.s are converted into Sphagnum- 

 hummocks through a displacement of the former by the latter moss; 

 and this is the end-product of the ant-hills. 



"The most general conclusion reached in the foregoing paragraphs 

 is that the ants play an important role in the formation of hummocks 

 in the bogs under consideration, since the hills serve as growth-foci 

 for the moss and peat vegetation. " 



Holmgren has also observed that in Lapland the nests of another 

 ant (F. ruja) are gradually overgrown by boreal plants (Vaccininm vitis 

 idcea, myrtillus and uliginosum and Riibns chamceinorus) . In this case 

 also the plants creep upward from the base of the hill, gradually driving 

 the ants to the summit and eventually extinguishing the colony. 



According to a footnote in the excellent work of my friend Dr. 

 K. Escherich of Strasburg^ a struggle between ants and mosses like 

 that recorded by Holmgren and myself seems to occur in certain 

 parts of Germany. He says: "Dr. A. Ludwig brought me from a bog 

 in Grunewald near Berlin a number of dried masses of Polytrichum 

 strictum, the basal half of which was perforated with chambers and 

 galleries. The inhabitants of these, a species of Myrmica, are driven 

 out by the increasing moisture due to the gradual intrusion of water- 

 storing Sphagna." Escherich also mentions similar observations 

 made by Kuhlgatz in the bogs of Western Prussia.^ 



Whether a similar displacement of ants by mosses occurs among 

 such American bog-ants as Myrmica rubra brevinodis, which, as I 

 have shown in a former paper,-' nests in hummocks of Polytrichum 

 commune, and Formica cvnerea var. neocinerea, which I have found 



1 Die Ameise. Schilderung ihrer Lebensweise. Braunschweig, 1906, 232 pp., 68 text-figs. 



^ Vorstudien iiber die Fauna des Betula nana-Hochmoores im Culmer Kreis in Westpreussen 

 Nordd. Wochenschr., n. F. I, 1002, p. 613. 



^ Ethological Observations on an American Ant (Lepthorax Emersoni Wheeler), Arch. f. Psvch. 

 u. Neurol., II, 1903, pp. 1-3 1, i fig. 



