TROUT 



cus which has caught a young trout. This 

 illustration is taken from a photograph of a 

 specimen lent to me by Mr. F. M. Halford, and 

 both the fish and the larva were alive when they 

 were caught. Unfortunately the trout is a little 

 shrivelled, and the legs of the Dytiscus have been 

 broken. D. marginalis lays its eggs in the stems 

 of rushes. The larva, when hatched, makes its 

 way out, and proceeds to lead a predatory life. 

 The larva when full-grown is about two inches 

 long, and is quite the most rapacious creature 

 which lives in our waters. The adult beetle is 

 also purely carnivorous, but is perhaps not quite 

 so rapacious. It would, however, probably at- 

 tack a larger fish. 



The largest of English water beetles is Hydro- 

 philus piceus. This beetle is not, in the adult 

 stage at least, carnivorous, but the larva, which 

 is about half an inch longer and considerably 

 fatter than that of D. marginalis, is carnivorous. 

 It may be told from the larva of Dytiscus not 

 only by its size, which is hardly a reliable point 

 for discrimination, but by the smaller size of the 

 head in comparison to the rest of the body. 

 The claws, with which HydropMlus seizes its 

 prey, are, too, considerably smaller than those of 



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