THE SPECIFIC CHARACTERS OF HYDROPORUS INCOGNITUS. 77 



On the Specific Characters of Hydroporus incognitus, Sharp 



{with plate). 



By FRANK BALFOUR BROWNE, M.A. (Oxon), F.R.S.E., F.Z.S. Director of 

 the Sutton Broad Laboratory. 



Since I published my first paper on the aquatic coleoptera of the 

 Norfolk Broads (Trans. Norfolk Norwich Nat. 8oc, vol. viii., part i. 

 p. 58, 1905), containing a list of the species I had found, I have more 

 than once been asked how I separated Hydmporus incognitus, Sharp, 

 from palustris, L., and have also been told by some who claim to be 

 authorities, that Dr. Sharp's characters are insufficient to separate 

 incognitus as a species from such a variable group as is included 

 under tbe name palustris. 



I did not pledge myself, in the paper referred to, to any opinion as 

 to the specific value of the names I used, but I satisfied myself, before 

 I published my list, that I could distinguish the species— or whatever 

 they might be — from published descriptions and type specimens which 

 were within my reach. 



However, after collecting a large amount of material, I have 

 thought it worth while to examine it carefully, with a view to 

 satisfying myself as to whether or not modern authorities are correct 

 in rejecting incognitus as a distinct species. 



H. incognitus was first recognised as specifically distinct from 

 palustris, in 1869, by Dr. Sharp, who published a description in the 

 tint. Mo. Mag., vi., p. 84, 1869, 70. He described it as "allied to 

 palustris, but larger, especially broader, with the pale markings less 

 developed, and not so distinct from the ground colour; moveover, the 

 whole is of a different form, and, in this respect, approaches erythroce- 

 phalus .... Punctuation of elytra rather more distinct than in 

 palustris, pubescence rather finer, and more sparing," and, he added, 

 " undoubtedly closely allied to }>alustris, but among a fine series of that 

 variable species I find nothing to connect the two." 



Thus the characters upon which Dr. Sharp originally relied were 

 the form, punctuation and pubescence. 



In 1881, Bedel (Coleopt. (hi Bassin de la Seine, p. 238) threw over 

 Dr. Sharp's characters, and relied upon others, as follows : — 



Hanches post : terries, a ponctuation peu reguliere et mal accusee .... 

 Tacbe basilaire oblique = palustris. 



Hanches post : assez luisantes, a ponctuation forte, serree, tres apparente 

 . . . . Tacbe basilaire des elytres transverse, contigue au bord anterieur, 

 jaunatre = incognitus. 



Bedel therefore relied upon two very doubtfully reliable characters 

 in separating incognitus from the variable palustris. 



In the Monograph of the Dytiscidae, published in 1882, Dr. Sharp 

 revised his description of incognitus, and referred to certain secondary 

 sexual characters thus : — " Mas, tarsis anterioribus leviter dilatatis 

 unguiculia vix innaqualibus," while, of }>alustris, he said, " Mas, barsis 

 anterioribus et intermediis dilatatis, ille unguiculis imequalibus, 

 anteriore crassiore et breviore." 



Now there is nothing in this description from which one can gather 

 whether the inequality of the claws is in reference to their length or 

 bulk, and I venture to suggest that a better term would be"dissimilis." 

 i.e., unlike, to describe the facts. I think also that Ganglbaupr's 

 description of the inner claw of palustris as "dicker und starker 

 April 15th, 1907. 



