116 GENERAL ZOOLOGY 



The animal life of any region is known as its fauna. 

 Though insects are widely distributed over the earth, a 

 study of the different species shows that there are more or 

 less well-marked areas, each of which possesses its charac- 

 teristic species. Though much overlapping occurs, as might 

 be expected in the case of animals which can fly freely from 

 place to place, yet on the whole it is possible to separate 

 fairly well-marked regions, the climatic and other bound- 

 aries of which have prevented any great intercommunica- 

 tion, thus producing peculiar forms of life in each region or 

 realm. Six realms are very commonly recognized (Fig. 68). 

 These do not exactly agree with the geographical divisions 

 into continents. The animal life of the Americas is fairly 

 distinct from that of the rest of the earth. Here two realms 

 are recognized, the Nearctic and the Neotropical. The 

 boundaries of the six realms are as follows : 



1. The Nearctic realm includes all Greenland and North 

 America south nearly to the tropic of Cancer. 



2. All Central and South America and the coastal region 

 of Mexico comprise the Neotropical realm. 



3. All Europe, Africa north of the tropic of Cancer, and 

 Asia south to an irregular line close to thirty degrees north 

 latitude is called the Palaearctic realm. 



4. The Ethiopian realm is that part of Africa south of the 

 Sahara Desert, Madagascar, and the southern tip of Arabia. 



5. The Oriental realm includes the tropical regions of 

 Asia, namely, India, Ceylon, and South China. 



6. The Australian realm is one of the most distinctive 

 because the animal life is so different from that of the 

 neighboring regions. This includes the continent of Aus- 

 tralia, New Zealand, and many of the surrounding islands. 



The student who has recently studied physical geography 

 may be able to see some relationship between the divisions 

 of these regions and climatic conditions. 



