332 THE WATER-RAT OR WATER-VOLE. 



under the wire-netting so that water-shrews and 

 rats could follow them, their presence was in no 

 way detrimental to the welfare of the young trout 

 in the ponds or of the spawn in the hatcheries. In 

 the end he allowed the voles to remain, as he 

 discovered according to his own evidence, which 

 quite satisfied him that they were effective in 

 destroying a particularly noxious dragon-fly larva, 

 which fed exclusively on the small and weakly fish. 

 One of these destructive creepers would sit on a 

 stone slab just where the water trickled into one 

 of the ponds, and immediately a young trout 

 drifted near it would propel itself forward by a 

 downward flip of the upturned, fin-like tail, catch 

 the fish in its powerful forceps, and drain its life in 

 a few seconds. After the coming of the voles the 

 remains of these hideous larvae were regularly found 

 on a stone slab above ; but it is still a very open 

 question whether they were destroyed by the water- 

 voles, or by water-shrews entering the wire-netting 

 by the creeps of the voles. If by the shrews, it 

 is at any rate refreshing to find that they did 

 something to pay their way. 



One or two naturalists refer to the water-vole's 

 partiality for fresh-water mussels, which it is said 

 to eat by gnawing a hole through the shell at one 

 side near the hinge ; but there seems insufficient 

 evidence to prove that this is the work of voles 

 and not of shrews, which, while very carnivorous in 

 their habits, are, moreover, very secretive. Water- 

 voles are regularly seen close to a place where 

 the empty mussel-shells lie about ; and since the 

 shrews are never seen there, their activities being 

 nocturnal, the natural conclusion is that the voles 

 are responsible. Further information bearing on 

 the water-vole's alleged carnivorous habits would 



