212 Flow to obtain it. 
larval stage it is not so often seen, but will be readily identified 
by the accompanying illustration. As will be seen, it is segmented, 
and when fully grown may be one and a half inches long, and is 
provided with a most cruel pair of jaws, resembling pincers in 
general form. It is not a particularly quick swimmer, but hunts 
from ambush amongst the sub-aquatic plants, and is one of the 
most destructive insects we have in our fish ponds. 
The perfect insect or beetle is an inch or more in length, and 
appears brown or purplish according to the lights, with a con- 
spicuous yellow marginal line. The under side is reddish brown. 
The only safe place for individuals of this species is among mature 
trout, which quickly and unceremoniously attend its funeral. As 
it leaves the water at will, and flies about in the air, and is 
nocturnal in its habits, we never know exactly where we have it, 
and it may come any night into our fry ponds. When, therefore, 
part of the torn body of a little trout is discovered some morning, 
it is time to keep a sharp look out for the enemy. These creatures 
sometimes account for a good many fish. We hear of cases in 
which trout fry in nursery ponds lessen in numbers unaccountably. 
The Dytiscus may be, and often is, the culprit. 
Fig. 29. Hydrophilus piceus and larva. 
Another insect belonging to the order Coleoptera, and to the 
ordinary observer something like Dytiscws, is the Hydrophilus. It 
is rather longer, and is more pointed “fore and aft,” and is 
harmless, being a vegetarian in diet, but it is not prolific, and is, 
therefore, of no great apparent importance to the fish culturist, so 
far as we know at present. 
There is another beetle which must be mentioned in passing, 
