108 



THE NORTH AMERICAN SPECIES OF DROSOPHILA. 



XII. GEOGRAPHICAL DISTRIBUTION. 



Table 9 shows the number of species of each genus of the Dro- 

 sophihna) known from each of the main geographical regions. The 

 Polynesian region is considered separately, because the data now 

 available indicate that for this subfamily the fauna is more distinct 

 from that of the rest of the world than is the fauna of any other region. 

 This fact is probablj^ due in large part to the incompleteness of the 

 data, for the word "Polynesian" in this case means practically "Hawai- 

 ian Islands." The parts of the Oriental region nearest to these islands 

 have not been well explored. Australia and New Zealand have been 

 included in the Oriental region, again perhaps only because of a lack 

 of data. These islands are practically unknown, so far as their 

 drosophiline fauna is concerned. The same situation is found with 

 respect to the relation of Madagascar to the Ethiopian region. 



Table 9 indicates that the Nearctic region is the poorest of all in the 

 number of species that it contains. The actual number recorded from 

 the Ethiopian region is somewhat less than that from the Nearctic, 

 but Africa has been very much less thoroughly collected than has the 

 Nearctic region. A discussion of each region in some detail follows 

 the table. 



Table 9. — Number of species of each genus in each region. 



NEARCTIC REGION. 



This region is characterized by the presence of the two endemic 

 genera Pseudophortica and Sinophthalmus. It has a relatively large 

 number of species that also occur in other regions. The five cos- 



