THE DIURNAL LEPIDOPTERA. 439 



All the great cosmopolitan genera, such as Fapilio, Pieris, Eu- 

 rema, &c., are represented in South America by whole groups often 

 of so much importance that they ought rather to be reckoned as 

 genera than groups. Again, many genera, like Apafura and 

 Thecla, which do not extend to Africa, are abundantly represented ; 

 while, on the other hand, Oatojysilia and Danaus, almost purely 

 tropical genera in the Old World, send out offshoots far into the 

 United States. This, however, is a parallel case to the occurrence 

 of Indian forms in Mantchuria, which in the west and centre of 

 Asia-Europe are ])urcly tro])ical. 



The Neotropical region is lar richer in llhopalocera than in 

 birds. Dr. Sclater estimates the birds at 2250 species, or one to 

 each 2400 square miles ; but the number of Ehopalocera already 

 known is not less than 4200, which is about equivalent to a spe- 

 cies to each 1310 miles. Nor is it likely that this enormous number 

 would be materially affected by tlie uncertainty as to how much 

 of Mexico should be included in the Neotropical region, as the 

 greater part of the Mexican species ai'e found in South America 

 also. 



I have not added a comparative Table of the number of birds 

 and butterflies in each region, as there are a considerable number 

 of species of the latter of doubtful locality not included in my 

 summary, and this can be better done when future discoveries 

 liave enabled us to check the rough results already arrived at in 

 a more perfect manner than is possible at present with our exist- 

 ing materials. 



[The following Table was prepared to illustrate the reading of 

 Mr. Kirby's paper, and is thcrclbre added here. — II.T.S.] 



Birds. Butterflies. 



Total number of species 7500 7700 



Europe, North Asia, Persia, Asia 1 p^^ p„^ 



Minor and North Africa J 



Africa, Central and Southeri 



dagascar, &c 



India and Indian archipelago 1500 1250 



Australia 1000 725 



North America 6G0 480 



South America 2250 4200 



eru,Ma-J^25Q 733 



