1906.] Wheeler, Relations of Ants to Plants 4^9 



actually watches the growth of a mound from its inception to its 

 decay. 



It would be important to know whether the above stages may be 

 detected in the development of the exsectoides nests throughout the 

 range of the species. Incidental remarks in McCook's work seem to 

 indicate that the nests in Pennsylvania present the same peculiarities 

 which I have described. He mentions (p. 254) twenty nests near 

 Warrior's Mark, in Blair County of that State, as " abandoned and 

 covered with moss and grass." And on page 256 he says : " Many a 

 romance of ant life lies hidden within those silent moss-covered 

 mounds." "I have thought that some of these abandoned hills 

 have been reoccupied as they carry a moss-grown and ancient appear- 

 ance, although in full activity. " 



For any observations corresponding to those recorded for the 

 Scotch Plains colony it is necessary to turn to the works of Euro- 

 pean writers. Europe possesses a species of Formica {F. exsecta) 

 which is not only so like exsectoides in color and structure as to have 

 suggested the name of the American species, but is also very similar 

 in some of its habits. These have been studied by Forel,^ Wasmann,^ 

 and more recently by Holmgren.^ 



F. exsecta lives in bogs and meadows, at lower altitudes in the 

 north but in southern Europe on high hills or mountains. According 

 to Wasmann, "The architecture of the nest is, generally speaking, a 

 small edition of that of the fallow ant {F. rufa) , both in regard to its 

 dimensions and the materials employed. It consists of much finer 

 substances, dried grass-blades, heather leaves, etc., and contains a 

 much greater admixture of earth. The heaped-up vegetable detiitus, 

 so characteristic of all so-called 'ant-hills,' forms in this case only 

 the top; beneath it lies a layer of densely felted grass-stems, grass- 

 roots and soil, in which the true galleries and the chambers of the nest 

 are excavated and whence they extend further down into the earth. 

 The form of the nest is that of a strongly truncated cone. Almost 

 never have I seen nests, either in Vorarlberg or in the Rhineland, 

 with an arched dome like that of F. rufa, but almost invariably only 

 such as had a flat top like that of F. pratensis. In mountain meadows 

 the cone is sometimes 50 cm. or more in height, its circumference i or 



' Les Fuurmis de la Suisse. Zurich, 1874, PP- iQi. ip*- 



2 Formica exsecta Nyl. und ihre Nestgcnosscn. Verhand. naturhist. Ver. Rheinl. Westf., 1804, 

 I Heft. 



■5 Ameisen {Formica exsecta Nyl.) als Hugelbildner in Siimpfen. Zool. Jahrb., Abth. f. Syst., 

 XX, 1904, pp. 353-370, 14 text-figs. 



