( 317 ) 



XIV. — On the Life-history of Hydrobius fuscipes, L. By Frank Balfour-Browne, 



M.A. (Oxon)., F.Z.S. (With Three Plates.) 



(MS. received July 6, 1909. Read July 12, 1909. Issued separately February 1, 1910.) 



In following out the life-histories of some of the water-beetles I have been struck by 

 the remarkable differences in habits and in structure between the members of a family, 

 for instance, between Hydro philus and Hydrobius, two fairly closely related genera of 

 the Hydrophilidse. The description of the life-history of Hydrophilus as given by 

 Miger, Lyonnet, and others will, only to a small extent, apply to Hydrobius, although 

 the suggestions which I am able to make with regard to certain facts in the life-history 

 of the latter may throw light upon somewhat similar facts in the life-history of the 

 former. 



Hydrobius fuscipes, L., is a very common water-beetle found throughout Great Britain 

 and Ireland in almost every stagnant piece of water where there is plenty of aquatic 

 vegetation, the favourite habitat appearing to be ditches or ponds where there is 

 abundance of grass growing in or floating out on the water. The beetle is small, 

 measuring about 6 or 7 mm. in length, slightly elongate, of a shining blue-black or 

 brown-black, although often in bright light showing a beautiful velvety-green lustre. 

 The legs in the typical form are reddish brown, the tibiae being tipped with darker 

 brown or black. 



There is a variety of this species which is either not very common in Britain or of 

 which collectors have not recorded their captures. This is H. seneus of Solier (Ann. Soc. 

 Ent. France, p. 314, 1834), and according to Rye is H. chalconotus of Leach (1814) 

 and of Stephens (Mand., ii. 128, 1829) (vide Ent. Mo. Mag., vii. p. 36, 1870-71). 

 Rye records having taken this variety at Barnes (Surrey), and Morley, C. (Coleoptera of 

 Suffolk, 1899) records it from " chalk pits at Little Blakenham (Suffolk, E.)." There is 

 a specimen in the collection of the late Mr Arthur Chitty which he took in 1887 at 

 Cuckfield Park (Sussex, W.), and recently Mr Donisthorpe took a specimen at Tottenham 

 (Middlesex) (Ent. Rec, xx., July 1908, p. 184), and he mentions that it has been 

 taken also at Sheppey (Kent, E.) and Woking (Surrey). It is recorded from Upper 

 Teesdale (Yorks, N.W.) (Vict. County History, 1907). Mr T. Stainforth tells me it is 

 common on the coast near Hull (Yorks, S.E.). I took a single specimen at Cambridge in 

 1904, and it seems to be not uncommon at "The Kinnegar," Holywood, Co. Down. 

 This variety apparently differs only in colour from typical H. fuscipes, and is of a 

 metallic blue or green on its upper surface, but the brightness of the colouring varies 

 greatly in different specimens and fades considerably after death. 



Thomson (Ann. de la Soc. Ent. de France, 1883, p. cxxxi.) separated as a distinct 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART II. (NO. 14). 49 



