242 BRITISH ANTS. 



of vegetable refuse, some construct earth mounds, others nest in 

 the ground, or under stones, and occasionally in tree stumps. 



The swarming of these ants is seldom seen, and some species 

 found their colonies in the normal, others in the abnormal 

 manners. 



Their colonies are generally large, some species possess branch 

 nests, and a great number of colonies in one area will all belong to 

 the same vast community. 



According to Wheeler Formica is "the most eury thermal " 

 of the circumpolar genera Stenamma, Myrmica, Lasius, and 

 Formica which are confined to the northern hemisphere, and it 

 ranges in Europe, Asia, and North America from a latitude of 30 

 to 60 or 65, and therefore nearly to the Arctic circle. In altitude 

 the species range from sea-level to above timber-line, 12,000 to 

 12 500 ft 



Wheeler [Bull. Mus. Compar. Zool. 53 385 (1913)] suggests that 

 North America is the original home of the genus ; he writes : " If 

 we divide the total number of the known Formicae (144) into Old 

 and New World forms, we find that Eurasia possesses only fifty-two, 

 whereas North America, though a much smaller land area, possesses 

 ninety-three species, subspecies, and varieties (one of the species, 

 F. fusca, is counted twice, because it occurs in both hemispheres). 

 This would seem to indicate that the latter continent must be the 

 original home of the genus, especially as it possesses representatives 

 of all the Eurasian groups of species besides two peculiar to 

 itself. 



Unless we accept the view that the genus arose in the polar region 

 during Mesozoic times and radiated its species out into Europe, Asia, 

 and North America, we must suppose that Eurasia has received its 

 species by immigration from the Nearctic region. That the latter 

 view is the more probable is shown by a glance at the distribution 

 of the forms in America. At least thirty-nine of our ninety- three 

 forms, or nearly 42 per cent, occur in Colorado and the adjacent 

 portions of New Mexico. Not only are these two states thus 

 abundantly supplied with species, subspecies, and varieties but the 

 colonies of the individual forms are unusually numerous and flourish- 

 ing on the mountain slopes of this territory. We may therefore 

 regard the southern ranges of the Rocky Mountains in the United 

 States as the center of origin of the genus and of the dispersal of 

 species to other portions of North America." 



Five species of Formica, some of which are closely related to 

 existing forms, have been described from the Baltic Amber. 



Lamarck [Syst. An. sans. Vert. 268 No. 124 (1801)] adopts 

 F. rufa L. as the type of Formica L. Latreille [Cons. Gen. Crust. 

 Ins. 311 No. 441, 437 (1810)] gives herculeana (L.) F., and rufa L., as 

 the types, and the latter was definitely cited as the type by Curtis 

 [Brit. Ent. 16 expl. PL 752 (1839)] Westwood [Mod. Class. Ins. 2 



