RODENTIA. 



227 



field-mouse is especially abundant in Europe, where it 

 sometimes multiplies so rapidly that it destroys whole 

 crops. It is as large as a common mouse, brownish 

 yellow on the back, and dirty white below. The water- 

 rat is about as large as the ordinary black rat ; it lives 

 on the banks of streams and ponds, and feeds on roots, 

 aquatic plants, frogs, insects, and little fish. 



FIG. 156. 



MUSQUASH (Fiber zibethicus). 



The lemmings have still shorter ears and tail than the 

 voles ; the body is heavier and the claws stronger. They 

 are about the size of the ordinary rat, and are found in 

 Siberia and Northern North America. In Northern 

 Scandinavia they multiply so rapidly that they periodi- 

 cally migrate in large numbers, swimming rivers, cross- 

 ing mountains, devouring whatever they come across, 

 and breeding and dying on the way. 



