September, 1901 



PSYCHE. 



245 



usually are. The nest was small. I 

 believe it necessary to be cautious and 

 to ask if the apparent association of differ- 

 ent species of Foniika is not also due at 

 times to the association of fertile females 

 of the two species. The fact could, on 

 occasion, be verified. At Hartford time 

 did not permit me to do this. 



In the suburbs of Boston (Franklin 

 Park) I found among others a Stnuiii- 

 geiiys, some Brac/iymynncx heeri, a Crc- 

 mastogaster, and a solitary worker of 

 Polyergus lucidiis, a fact wiiich is as- 

 tonishing if one considers that the lati- 

 tude of Boston is nearly 45° N. [more 

 nearly 42° 20'] (nearly the same as 

 Turin) , and that it is much colder than 

 in the same latitude in Europe. Now 

 these genera of ants love heat. 



In the old world the number of 

 species is less in continental than in mar- 

 itime climates. Thus the ant-fauna of 

 Bulgaria is much scantier than that of the 

 south of France. Besides, the fauna there 

 is upon the whole less southern. But it is 

 necessary to take into account other fac- 

 tors without which one cannot understand 

 why the fauna of North America, in 

 spite of the continental climate of the 

 country, is so much richer than ours. 



However, one finds, even with us, 

 some exceptions. Thus Myrmccocystua 

 riaticus, a .southern form, extends far- 



ther north in eastern Europe (continen- 

 tal climate) than in western Europe 

 (maritime climate). This species, there- 

 fore, stands a rigorous winter well pro- 

 vided it has a hot and dry summer, 

 while with others it is for the most part 

 the contrary. But it is evident that for 

 America there are some facts of pre- 

 historic geological geography which 

 have contributed to preserve there a 

 fauna and flora very much richer than 

 in the Old World. This fact is well 

 known and of great interest, considering 

 tiie close relationship between the ne- 

 arctic (North American) fauna and flora 

 on the one side and the palearctic (north- 

 ern Old World) fauna and flora on the 

 other, a relationship which is antecedent 

 to the glacial epoch, when the two 

 faunae were connected by Greenland. 

 Moreover, one observes some facts in 

 America analogous to those of the Old 

 World. Thus North Carolina has in 

 its western part a distinctly continental 

 climate, while in the east the Gulf Stream 

 gives it one of somewhat maritime char- 

 acter. Now, the ant-fauna of the state 

 is much richer in the east than in the 

 west. It is true that the western part is 

 also somewhat more elevated ; but the 

 mild winter is without doubt the principal 

 cause of this wealth. 



