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. Camponotus whympert, 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 
earinae short, subparallel, not diverging behind. Stipes of 
male genitalia much longer than the volsellae and sagittae. 
Small, mostly smooth, shining, dark-colored species. 
Subgenus Prorormica 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 Linné. 
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........... a. 
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. 
