—— 
No. 10.— A Revision of the Ants of the Genus Formica (Linné) Mayr. 
By Wituiam Morton WHEELER. 
No revision of the American ants of the cireumpolar genus Formica 
has been published for many years, notwithstanding the fact that it 
comprises some of the most important members of our insect fauna. 
Mayr,2 who in 1886 first attempted a revision of this genus, cited only 
seven species and seven varieties from North America. We are in- 
debted to Emery, however, for the first really serious account of these 
ants. In 1893 this investigator gave us, in a very succinct and admir- 
able paper,’ a critical account of all the known American forms, on 
the basis of collections made by Mr. Theodore Pergande and Rev. 
P. J. Schmitt. In this paper eight species, twelve subspecies, and 
fifteen varieties are recognized as being peculiar to our fauna. During 
the twenty years that have since elapsed a much greater amount of 
material has found its way into public and private collections, and 
during the past thirteen years I have described several species and 
have accumulated both through my own efforts and through the very 
generous aid of many correspondents so large a collection of Formicae, 
that it seems advisable again to “take account of stock”’ of the North 
American forms. A study of all this material enables me to recognize 
thirty-one species, nineteen subspecies, and forty-three varieties as 
belonging to our fauna. Since many of these are very closely 
related to the Palaearctic or Eurasian forms I have included a brief 
account of the latter in the present paper. In this part of my work 
I have made extensive use of Emery’s recent revision of the Palae-- 
arctic ants.* 
The species of Formica can be readily distinguished from the species: 
of the other genera of the subfamily Camponotinae by the following 
characters :— 
The workers are small or medium-sized ants, often varying consid- 
t Contributions from the Entomological Laboratory of the Bussey Institution, 
Harvard University. No. 59. 
2 Die formiciden der Vereinigten Staaten von Nordamerika. Verh. Zool. bot. ver. 
Wien, 1886, 36, p. 419-464. 
* Beitrige zur kenntniss der nordamerikanischen ameisenfauna. Zool. jahrb. Syst., 
1893, 7, p. 633-682, 1 pl.; 1895, 8, p. 257-360, pl. 8. 
‘ Beitrage zur monographie der formiciden des paliarktischen faunengebietes. 
(Hym.) Teil. 7. Deutsch. ent. zeitschr., 1909, p. 179-204, 16 figs. 
