PLAGUES OF FIELD MICE 
all winter, but otherwise it digs a tiny tunnel and hibernates 
underground. A singular mouse of the desert region has so 
very spiny a fur that ‘‘when it has its spines erected it is al- 
most indistinguishable from a diminutive hedgehog.” Another 
desert genus imitates the jerboa in form and habits; and the 
Barbary mouse is prettily striped. Peculiar genera are restricted 
to various African and Asiatic regions, or to single East Indian 
islands (bamboo rats); and Australia possesses several species 
— the only native mammals not marsupials except bats. One 
of them is the beaver-rat—a large dark brown species of 
Hydromys frequenting creeks like the European water rat, and 
having a beautifully soft, beaverlike skin. 
The water rats proper, the ‘‘voles” of the English, form a 
group with many representatives in the United States, and are 
of rather stout, clumsy build, with short ears and short hairy 
tails. The water rat and bank vole are familiar ones in Great 
Britain, dwelling in holes in every stream bank, and swimming 
in ponds, though their feet are not webbed. Another very 
small vole is the ordinary field mouse of Europe, which every 
few years, by reason of plentiful food and other favorable con- 
ditions, suddenly becomes excessively numerous in some region 
and appears as a “plague.” Millions of these mice will dev- 
astate the local fields for a year or two, and then. gradually, 
by enemies and disease or starvation, will fall away to their 
original numbers. In South Russia, Hungary, and similar 
countries, such plagues have sometimes caused extensive 
famines. The same thing has happened in Nova Scotia, and 
is liable to arise in our prairie states. 
To this group belong our short-tailed meadow or field mice, 
wood mice, pine mice, lemming mice, and muskrats. 
The meadow mice (genus Microtus) exist in many species 
and varieties all over the continent north of the Tropics. 
“They live,” says Miller, “in an endless variety of situations, from sea 
beaches to marshes and alpine mountain tops, and from open plains to 
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