ini ADEPHAGA. \Il ijdroporiua. 



beginning to work the British species to treat the genus Hydroporus as 

 a whole, as inckiding (according to the old arrangement) Bidessus, 

 Coeknnlms, Deronedes, and Hydroporus, and to work them from the 

 specific descriptions ; Hydrovatus is easily separated by its round shape 

 and the ])ointed apical angle of elytra, and Hyphydnis by its very ovate, 

 thick form, and the unequal claws of the posterior tarsi : the Hydroporina 

 as a whole may be known (as far as our fauna is concerned) from the 

 rest of the Dytisci complicati by their small size, four-jointed front 

 tarsi, and invisible, or almost invisible, scutellum. 



£ZVI>ROVATUS, jMotschulsky. {Oxynoptiliis, Kies. pars.) 



This genus com^^rises about forty species from various parts of the 

 world ; three only occur in Europe, of which we possess one, which has 

 (july, as far as I know, occurred at Portsmouth ; in certain species the 

 males have several joints of the antennae irregularly dilated, and in 

 others they are furnished with a stridulatory organ at the junction of 

 the posterior coxse and metasteruum. 



H. clypealis, Sharp. Very short, ovate, almost round, dark ferru- 

 ginous, with the head and thorax lighter, sometimes entirely light 

 ferruginous ; head and thorax almost smooth, elytra somewhat coarsely 

 and diti'usely punctured with apex pointed; antennae short, joints 4-10 

 diifering but little from one another, in the male transverse, in the 

 female about as long as broad. In the male the basal joints of the front 

 and middle tarsi are much dilated. The female is alutaceous and dull, 

 the male shining. Long. 2^-2i, lat. li mm. 



Portsmouth, in a pond on the north side of the Island of Portsea, taken abundantly 

 by Mr. Moncreafl". 



This insect was at first referred to 0. cusj^idatus, Kunze, by Mr. Crotch, 

 but it is rather smaller, and is distinguished bj^ its anteiinal characters, 

 the less distinct punctuation of the upper surface, and the much less 

 closely and regularly punctured coxae. 



BIDESSUS, Sharp. 



In this genus the prosternal process is larger than broad, parallel- 

 sided, l)ut with a more or less acute extremity ; the middle coxae touch 

 one another ; the posterior tibise have the basal portion much more 

 slender than the apical one ; the number of species is about eighty, 

 which are found in most parts of the world ; they are all very small 

 (from 2 to. 3 mm. long) ; three only are found in Great Britain, which 

 may be distinguished from the other members of the old genus Hydro- 

 porus by having a plainly impressed stria on each side of thorax which 

 is distinctly continued on the base of the elytra. 



I. Sutnral stria efl'aced behind middle, or entirely wanting, 

 i. Elytra rather convex, black or jiitch-brown, at most 



with a few reddish spots on outer margin . . . . B. ITNISTEIATUS, Sclir. 



