GREAT BLACK WATER & ROVE BEETLES 



it leaves the water-margin, and excavates a small oval- 

 shaped cell in which to remain concealed. Under 

 normal conditions it doesn't take long for the perfect 

 beetle to emerge, but there are times when it remains 

 in the pupal state throughout the Winter. The adult 

 extrudes its hind quarters above the surface of the water 

 so as to take in a fresh supply of air bubbles. 



The Great Black Water Beetle {Hydrous piceus), must 

 not be confused with the last-mentioned, as, in the 

 adult state, H. piceus appears to be a vegetarian. It is 

 the largest member of the Coleoptera in Britain, with 

 the sole exception of the handsome Stag Beetle. The 

 female deposits a number of eggs in an oval cocoon 

 which she cleverly attaches to an aquatic plant. The 

 larva feeds upon animal food until such time that, for 

 some reason, it decides to become a vegetarian ! This 

 species is harmless in an aquarium and may much more 

 safely be recommended than Dytiscus tnarginalis. It 

 belongs to the Family Hydrophilidce. The Staphyltntda, 

 or Rove Beetles, are next in order of merit as regards 

 the family tree, but must be summarily dismissed with 

 the statement that they include a very large assembly 

 of small species which, although good fliers, fold their 

 wings into a very small space, and have very short wing- 

 covers. Those with which the reader is most likely to 

 come into contact are the annoying little insects which 

 have such an obnoxious habit of getting into one's eye, 

 and causing painful irritation until removed. These 

 unwelcome visitors are all popularly dubbed " Flies " 



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