IS-: ANTS. 



clearly the case with C. pinna! us, which occurs in the United States 

 only at the southern tip of Florida and in southwestern Texas. 



It is not so ea^\ to account for the distribution of species of a few 

 tropical and subtropical genera like Po^oiioinyniie.v, Ercbomynna and 

 J'licidolc within the L'nited States. Pogonomyrmex is a peculiarly 

 American genus ranging from Montana to Argentina. It is repre- 

 sented in the Southwestern States by a number of species, one occurs 

 in Florida and ( ieorgia and at least one in the West Indies. The south- 

 eastern species (P- badius) differs from all the others in having poly- 

 morphic workers, the West Indian form belongs to the subgenus 

 Ephcbom\nnc.\-, which is also represented in Brazil, Mexico, Texas and 

 Arizona. Recently the number of known South American species of Po- 

 gonoin\niic.r has been considerably augmented (Emery, 1905/7). The 

 question arises as to whether this genus had its center of origin in South 

 America and radiated its species northward or whether it arose in the 

 southwestern center of North America and extended thence southward to 

 Argentina. The former supposition is supported by analogy with the ad- 

 vent of so many South American forms in North America, the latter by 

 the fact that Pogonomyrmex is closely related in structure, though not in 

 habits, with the boreal genus Mynnica. Of Erebomyrma only a single 

 species ( E. longi of Texas) was known till recently, when Emery 

 described another (E. peruviana) from Peru. This genus, too, is 

 probably of South American origin. This may be inferred from the 

 fact that the allied genera Tranopclta and Carebarella are exclusively 

 neotropical. Moreover, the allied genus Solenopsis is represented by a 

 much greater number of species in South than in North America. The 

 genus PJicidolc is widely distributed and represented by numerous 

 species in the Southeastern and Southwestern States and a few species 

 (Ph. Tuiclandica, tysoni, pilifcra) have spread into the Northern States. 

 Most of the North American species are quite distinct and may be 

 regarded as endemic. I know of no species common to the West 

 Indies and the southeastern center, and although many southwestern 

 species occur in northern Mexico they seem to be for the most part 

 quite distinct from the southern Mexican and South American species. 

 As the genus is cosmopolitan it is not improbable that our species 

 may be derived from relicts of Mesozoic forms that were preserved 

 in the southeastern and southwestern centers during glacial times. 

 Perhaps further studies of the Mexican and West Indian, and espe- 

 cially of the Cuban and Ilaytian species may throw some light on the 

 American distribution of this interesting genus- 



A few words must be said about the 'ants that have been imported 

 into North America by commerce, for although these comprise a com- 



