948 THE AMERICAN NATURALIST. (VoL. XXXVI. 
European specimens by Professor Emery, who reported as 
follows (zz Zferis): ‘It is the true European form, differing 
from our common type only in the total absence of erect hairs 
on the thorax. In this respect it approaches var. glauca 
Kusgky from Oriental Russia." It is possible that Dr. Mayr 
may have seen specimens of this same ant, but it is more probable 
that he had specimens of zeo-rufibarbis Emery, a common form 
throughout the more western and southwestern states as far 
.. as the Pacific coast. The specimens of cinerea received from 
Dr. Heath were compared with European cinerea given me by 
Professor Emery, Professor Forel, and Dr. Mayr. The speci- 
mens from Professor Emery were collected near Bologna, Italy. 
They are decidedly smaller and have a darker ground color 
than the Californian specimens. These, however, agree very 
closely in their larger size and somewhat reddish coloration 
with the Austrian and Swiss specimens from Dr. Mayr and 
Professor Forel. I believe, therefore, that there can be no 
doubt concerning the occurrence in California of two species 
of Formica almost or quite identical with the European cinerea 
and rufibarbis. It is not so easy to decide whether one or both 
of these species are imported or indigenous to the American con- 
tinent, but I know of no cogent reasons for accepting the former 
alternative. Certainly the occurrence of these species on the 
Pacific coast and their apparent absence from the eastern states 
of our Union are extremely suggestive in connection with 
the like geographical distribution of many other Pacific coast 
arthropods (Astacus, e.g., many Diptera, and other insects) 
which are known to be more closely related to European genera 
and species than to those of the Atlantic states.! 
After accustoming myself to view the distribution of the 
two species of Formica in this light, I was much surprised 
during August of the past summer to find cinerea very abun- 
dant in the vicinity of Rockford, Winnebago County, Ill. For 
several weeks of three successive summers I had collected very 
diligently without finding any such species in this locality. It 
1 See,zg., Osten Sacken's “ Western Diptera.” Cases in point are also the 
Californian ants of the subgenus Messor, and Myrmica mutica Emery, which is 
hardly more than a subspecies of the European M. rubida. 
