WHEELER: ANTS OF THE GENUS FORMICA. 427 
Host (Temporary). Ff. fusca. 
North and Middle Europe, south as far as the Pyrenees and south- 
ern slopes of the Alps; Caucasus, Siberia; occurring only in the moun- 
tains in Southern Europe. 
The typical F. rufa constructs large mound-nests of vegetable 
débris, usually pine-needles, in open forests, preferably of coniferous 
trees. A single colony may have several of these nests, which are con- 
nected with one another by run-ways. New colonies (not new nests!) 
are formed, as Wasmann and I| have shown, by temporary social para- 
sitism, the recently fecundated female finding a home in a F. fusca 
colony and permitting these ants to bring up her young. The fusca 
queen is either destroyed by the intrusive rufa queen or by her own 
offspring, so that when the fusca workers eventually die off, a pure 
colony of rufa remains. New nests are formed by adoption of rufa 
queens which leave the parental formicary with detachments of 
workers. 
The forms F. polyctena Forster and F. piniphila Schenck are based 
on specimens which differ somewhat from the typical form in pilosity; 
polyctena having the head and thorax almost hairless, whereas pina- 
phila is more pilose. 
21. F. RUFA RUFA Var. MERIDIONALIS Nassonov. 
F. rufa var. meridionalis Nassonov, Arb. Lab. zool. Univ. Moskau, 1889, 4, 
p.17, 8 ; Ruzsky, Formicar. Imper. Ross., 1905, p. 330; Emery, Deutsch. 
ent. zeitschr., 1909, p. 186. 
Worker. Differing from the typical form in color, the red parts 
being brownish yellow, the legs brown. Hairs very sparse. 
Siberia. 
It is not impossible, as Emery seems to imply, that this variety may 
be based on immature specimens of the typical pratensis. 
22. F. RUFA RUFA var. RUFOPRATENSIS Forel. 
F. rufa var. rufopratensis Forel, Denks. Schweiz. gesell. naturw., 1874, 26, 
p. 53,8 2 o&; Emery, Deutsch. ent. zeitschr., 1909, p. 186. 
WorkKER and MALs transitional in color and pilosity, and FEMALE 
in the smoothness of the gaster, between the typical rufa and the sub- 
species pratensis. These various characters are combined in the most 
manifold manner and degrees in different specimens. 
