1 1 s AN 'IS. 



by the annectant genus . Inciirctus, still living in Ceylon, and the genera 

 /'rotancitrctiis and J\iraiicitrcfns. which 1 have detected in the Baltic 

 amber. The Camponothue are a thoroughly cosmopolitan group, 

 though represented by the greatest variety of types in the ( )ld World. 

 They must have- arisen from the Ponerinae at a very remote period 

 during Ak-Mixoic times, it is very probable that the separation of the 

 Indian from the South American region preceded the development of 

 certain peculiar tribes among the Myrmicinae and Camponotinae since 

 \ve find the singular Cryptocerii and Attii confined to the American 

 tropics, whereas, the Indian region has the Cataulacii, Polyrhachis, and 

 several remarkable Camponotine genera. The Tetramorii, too, are 

 almost exclusively Indo-African, being represented in America only 

 by a few more or less aberrant species. 



The north temperate regions both in Eurasia and America seem to 

 have remained long enough in connection with the Indian region to 

 acquire an admixture of types from this source. Purely north tem- 

 perate elements are the genera Formica, Polyergus, Lasius, Myrmica, 

 Stcnamma s. sir. and certain species of Lcptothora.r (acervorum} and 

 Ciiinponotns (hercitleanus). Europe acquired its species of Mono- 

 inoriitni, Tetramoriuwi, Cremastogaster, Plagiolepis. Acantholepis and 

 Bothriomyrmex from southern Asia, and North America received its 

 species of Monouwrium and Cremastogaster from the same source. 



The history of the North American ant-fauna deserves somewhat 

 fuller treatment. This fauna, which during preglacial times was prob- 

 ably exceedingly rich in genera and species, must have been largely 

 exterminated when the northern portion of our continent was buried 

 under the great ice-sheet. Further southward a few of the more 

 warmth-loving forms managed to survive, where they have persisted 

 as relicts, while somewhat more numerous remnants of the ancient 

 preglacial arctic fauna survived along the edge of the ice-sheet or 

 possibly on small non-glaciated islands farther north. South of the 

 ice-sheet the survival of the old forms was greatest in the Sonoran 

 province, /. c., in Northern Mexico and the Southwestern States. This 

 seems to have been an arid region even at that time and was, therefore, 

 warmer than the more humid southeastern portion of the continent. 

 The recession of the ice-sheet at the close of the glacial epoch \vas 

 followed by a northward migration of the ants. This appears to have 

 taken place in much the same manner as Adams has described for 

 other North American animals and plants : ' The returning biota fol- 

 lowed, in all probability, a definite successional relation and was com- 

 posed of three general belts or ' waves,' concentrically distributed south 

 of the ice margin. The first one was of the barren ground type, the 



