wheeler: ants of the genus formica. 387 



our biogeographical and geological conceptions, it is timely to call 

 attention to the fact that the boreal distribution of the species of 

 Formica, especially of the typical F. fusca, is in complete accord with 

 the views of Kolbe and Scharff . This is also true of certain other ants, 

 e. g. Campofwtus whymperi, Lasius niger and several of the species of 

 Myrmica. 



In order to facilitate the identification of the various species, sub- 

 species, and varieties of Formica, I append dichotomic tables of the 

 worker phases. I have added tables of the females of the rufa and 

 microgyna groups, because their females are usually much more easily 

 identified than their workers. It is often difficult or impossible to 

 identify isolated Formica workers or specimens that are not perfectly 

 clean and well preserved. For this reason the collection and descrip- 

 tion of single worker specimens of these ants, as if they were but- 

 terflies or beetles, should be discouraged. 



KEY TO THE SUBGENERA AND GROUPS. 



1. First funicular joint of worker and female about as long as the 



second and third joints taken together, the latter shorter or 

 at least not longer than the penultimate joints. Frontal 

 carinae short, subparallel, not diA'erging behind. Stipes of 

 male genitalia much longer than the volsellae and sagittae. 

 Small, mostly smooth, shining, dark-colored species. 



Subgenus Proformica Ruzsky. 

 First funicular joint of worker and female distinctly shorter than 

 the second and third joints taken together, the latter longer 

 than the penultimate joints of the antennae. Stipes of male 

 genitalia but slightly longer than the volsellae and sagittae 

 except in the subgenus Neoformica. 



2. Subgenus Formica Linne. 



2. Anterior border of clypeus of worker and female, and often also 



of the male, notched or emarginate in the middle. 



sanguinea group. 



Anterior border of clypeus of worker, female and male entire, 



rounded or subangularly produced in the middle 3. 



3. Sides of head subparallel, posterior border deeply and broadly 



excised in the worker and female and often also in the male. 

 Basal border of mandibles with vestiges of denticles. 



exsecta group. 



