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HYDROBIUS FUSCIPES; 

 NOTES ON ITS LIFE-HISTORY, LARVAL ANATOMY, ETC, 



WALTER F. BAKER, F.E.S., 

 Whitkirk, Leeds; late Hon. Secretary of the Yorkskirc Naturalists' Union. 



The following is a brief account of the life-history of one of our 

 common aquatic beetles, and is given, not only as a contribution to 

 entomological literature, but also in the hope that it will induce 

 others to pay more attention to the life-histories of the various 

 creatures whose distribution they are studying. I have no intention 

 of under-rating the work done by the systematist — far from it — for 

 the facts of distribution are quite as important in their way as any 

 other facts, and throw light upon many points that would otherwise 

 be obscure ; but my meaning is, that instead of naturalists devoting 

 their whole time to enlarging their collections and studying the 

 distribution of insects in their own particular neighbourhood, they 

 should extend their researches into the equally attractive and less 

 known study of life-histories. Another class of naturalists who 

 might with advantage turn their attention to this branch, is the 

 so-called microscopist, who, whilst possessing a good instrument and 

 the usual accessories, yet contents himself with buying his slides, 

 and is always ready at a microscopical conversazione to show the 

 ever-present stock objects, such as ' wing of butterfly,' ' diatoms,' or 

 the ' human flea.' Very little is known of the early stages of many 

 of our commonest insects, and though it necessitates constant and 

 careful watching, yet it is a comparatively easy branch of natuial 

 history, and will well repay tJTe student. 



This little beetle, Hydroblus fuscipes (Fig. i), is one of the 

 commonest, if not the most common, of our aquatic beetles. It 

 varies very considerably in size. Down in the 

 marshes of North Lincolnshire and Nottinghamshire 

 I have often obtained specimens measuring as 

 much as 8 mm. in length, but most of the speci- 

 mens I have obtained in Yorkshire are not more 

 than 6| mm., and they are occasionally found less 

 still. It is hardly possible that this is owing to 

 climatic distinctions, as the difference is so slight, p. ^ 



neither is it owing to scarcity of food, for though Hydrobius fuscipes x 3 

 the fens of Lincolnshire may be a more ideal spot for it than the 

 more thickly populated and less marshy county of York, yet there 

 cannot be any real insufficiency of food, for it is not at all particular 

 in this' respect, and I have kept them alive for nearly a year by 

 feeding them on nothing but duckweed. Whether they are entirely 



