XV A PLAGUE OF VOLES AVM], 
They have, in the case of the first three, transverse ridges, from 
which stand up two sharp and long tubercles. The other teeth 
have two ridges. The incisors are pale yellow. The shape of 
the teeth and the smallness of the caecum suggest that this 
Rodent is not so purely a vegetarian as others, and that it 
nourishes itself largely upon insects. 
Sub-Fam. 8. Microtinae—The Voles or Water-Rats form a 
distinct group of Murine animals, to which the sub-family 
name of Microtinae has been applied from the genus MJicrotus 
(more generally known as <Arvicola), a genus which includes 
the Water-Rat and Field-Voles of this country. This genus 
has short ears, and a short and hairy tail. Its build is 
stouter and clumsier than that of the Rats. The genus is 
confined to the Palaearctic and the Nearctic regions. In this 
country there are three species. The best known is the Water- 
Vole or Water-Rat, JZ amphibius, which has been seen by 
most people, and which frequents streams, ponds, and canals. 
The feet, curiously enough, are not webbed, which seems to 
argue the recent adoption of an aquatic life. Mr. Trevor- 
Battye has remarked that this animal, when swimming at 
leisure, uses its hind-limbs only, carrying the fore pair at 
the sides like a Seal. The Bank-Vole, JZ glareolus, is rather a 
local species in this country. It is a terrestrial Vole, and 
burrows. The Field-Vole, JZ agrestis, has become notorious on 
account of the “plagues,” to which its immense numbers have 
on occasions given rise. It is the smallest species, and has a 
greyish-brown fur lke the Water-Vole, the Bank-Vole being 
redder. ‘To give an idea of the cost of the depredations of this 
animal, Mr. Scherren quotes! a farmer who gave evidence before 
the Agricultural Commission to the effect that, putting the 
damage of one Vole at two pence, the amount of loss suffered on 
a farm of 6500 acres in two years would be £50,000! 
The genus Fiber comes very near the last. It is a North 
American genus. The hind-feet are slightly webbed; the tail is 
a trifle shorter than the body, and is compressed and scaly, with 
scattered hairs. The thumb is short, but with a fully-developed 
claw. As in the last genus, the small and large intestines are 
roughly of the same length, and the caecum is about one-fourth 
of the length of either. It is known as the “ Musquash.” 
1 Popular Natural History of Animals, London, 1898. 
