( cviii ) 



The New 'World lias 54 genera which do not occur outside it ; 10(i are 

 peculiar to the Eastern Ilemispliere ; while 7 are common to both. The pro- 

 portion between genera and species is,- therefore, nearly the same in either 

 hemisphere. Taking into account the origin of the genera as shown in the 

 following pages, and leaving aside the truly cosmopolitan Celerio, there are 53 

 genera of American extraction, against 113 of Old World origin. 



Some significant discordance will be found in the numerical distribution of the 

 genera and species when comparing the two tables (pp. cv. and cvii.). The Western 

 Hemisphere has one and a half times as many species of Aclterontiinae as the 

 OKI \Vorld, but they are more uniform, belonging only to 16 genera; whereas 

 the s]iecies of the Eastern Hemis])here are groujied in 27 genera, representing 

 many more ste{).^ in the development of the AcheroHtiinae than do the Trans- 

 atlantic forms. On the other hand, the 26 Old World species of Sesiinae belong 

 only to 3 genera, while America possesses 22. In Choerocampitme America, with 

 its 3 genera, of which 1 is cosmopolitan {Celerio), stands far behind the Old 

 World, which has 12, though the proportion of the species is 53:85. 



The difference in the pro]>ortion of tiie species and genera is instructive in 

 another resjiect. Looking at tlie table of genera, it will be manifest that the 

 student of geographical distribution who bases his conclusions on the Sesiinae 

 alone would have only one centre of development, which has given off a few 

 branches to other countries ; tliere would be no tpiestiou of " Regions." If he 

 took the Vhoerocampinae as tiie basis of his zoogeograjihical division of the 

 earth, Aethiojiia and Indo- Australia might become Regions and the rest of the 

 globe appendages of them. If lie based his exposition on the Fhilampelincie, 

 Africa, Indo-Australia, and Nortli America would rank as Regions, and South 

 America, Europe, and temperate Asia ai)pear to be zoogeographical appendages of 

 them. While in tlie case of tlie Arheroiitiiiiae there would be four Regions. It 

 is evident fiom this that the division of the globe into zoogeographical Regions 

 is different according to wliicli group of animals is taken as the sole basis of 

 the division, or, in other words, that the division which is correct in one group 

 of animals does not necessarily apply to every other group. That the Neotropical, 

 Aethiopiau, and Oriental Regions are nevertheless natural zoogeogra[)hical 

 districts in all larger groups of land and f'lesh water animals is not to be 

 wondered at, since these Regions comprise each the subtropical and tropical 

 ])arts of a continent and its satellites of islands. America north of Mexico 

 and Europe and temperate Asia are by no means so well characterised as, and 

 co-ordinate to, the other three Regious. 



In tlie above tables of distribution we have included the Papuan Sjthingidae 

 in the Orieutal fauna. Australia, New Guinea, the islands farther east, and 

 those westward to the Moluccas have 26 genera of Hawk Moths, of which 

 liave not been found elsewhere. The Palaearctic Region has 7 peculiar genera 

 out of 3(J. These figures alone would show, therefore, that the Papuan countries 

 were as much entitled to the rank of a Region as the northern temperate Old 

 World zone ; or, on the other hand, since the proportion of genera peculiar to 



