II 



GEOGRAPHICAL DISTRIBUTION OF 

 THE HOUSE MOUSE 



The great order of Rodents or gnawing mammals is very 

 successful as judged by the extent of its distribution and the 

 degree of its adaptation to varied environments. Cavies 

 scuttle under brush, rats slink about human habitations, 

 mice squeeze through inconceivably small holes, squirrels 

 scurry up trees and leap or glide from branch to branch, 

 rabbits tunnel the earth, amphibious beavers fell trees and 

 build dams. Yet all are hopelessly dependent upon their 

 chisel-like incisors, which proclaim a common relationship 

 and give them a common name. 



The five families of rodents enjoying the widest distribu- 

 tion (7) l are the Leporidse (rabbits, hares), the Hystricidse 

 (porcupines), Sciuridse (squirrels), Cricetidae (New World 

 mice, meadow mice, hamsters), and the Muridae (Old World 

 rats and mice having tubercular teeth). 



Because the rabbits have four incisors in the upper jaw 

 and two in the lower, they have been assigned to the sub- 

 order Duplicidentata (duplex-toothed) or even made a 

 separate order, Lagomorpha. The porcupines, squirrels, 

 rats, and mice bear two incisors both above and below and 

 are placed in the sub-order Simplicidentata (simple-toothed). 



Of these successful families the last two have attained 

 world distribution, while the other three had established 

 themselves before modern times in all geographical regions 

 except the Australian. 



The accepted classification of the common house mouse is : 



Order Rodentia (gnawing animals) 



Sub-order Simplicidentata (simple-toothed) 

 Family Muridre (mouse-like animals) 

 Genus Mus (true mice) 



Species musculus (the little mouse) 



1 Italic figures in parentheses refer to names listed numerically in the Bibliog- 

 raphy at the end of the text. 



4 



