﻿1869.] 161 



As far as my own experience goes, I may remark that I have never found P. 

 Julinii except in the company of P. Pollux (though the converse does not hold 

 good), and that I find the thoracic outline, and size, &c, of the punctures of the 

 stria? and of the interstitial scales do not afford constant diagnostic characters. — Id. 



Notes on certain British Hydropori recently brought forward by Dr. Sharp. 



Hydkopokus obsoletus, Aube. I have in my collection two examples of this 

 species : one given me by Dr. Power, the other taken by myself at Gosforth. 



H. Nigbita. I am very much inclined to think that the two insects separated 

 by Dr. Sharp [Entomologist's Monthly Magazine, Vol. vi, p. 82], are only the 

 sexes of one and the same species ; the glossy, strongly punctured, pubescent one 

 being the male, and the obscure, less punctured, nearly glabrous one, the female. 

 I have the species from the south of England, and it has occurred to me in several 

 localities in Durham and Northumberland, rather sparingly, and copiously in 

 Cumberland, where it affects the runners from spring3 on the moors. In every 

 one of these instances the two forms were taken in company, and in nearly equal 

 numbers. This, I think, would not have been the case, had they been distinct 

 species. The last time I met with this species was on a moor near Lanercost, in 

 July, when I took about one hundred individuals. This series furnished me with 

 varieties of both forms, principally in dilatation of the sides of the thorax, in the 

 apices of the elytra, and in sculpture, colour, and pubescence ; in both sexes the 

 paler-coloured examples are the most thickly furnished with hair. The general 

 shape is the same in all, the fovea on the clypeus in all is alike, the margins, and 

 angles of the thorax are also alike, whilst the antenna? and legs are similarly 

 maculated with fuscous. 



Surely, Herr Thomson, when he wrote his " Conspectus Specierum," (Skand. 

 Col., ix, 73] must have had some other species in view, for he places pubescens 

 (nigrita, Shp.) in a section of which he says " prothorax lateribus crasse marginatus ;" 

 whereas, in both sexes of our nigrita, the thorax is very finely margined at the 

 sides. 



By the kindness of Mr. Crotch, I have examined a pair, $ $ , of PL. discrehi-s, 

 Fairm. The male is a little larger, a little wider in front, somewhat less convex, 

 but much more finely and closely punctured than any male nigrita ; the pubescence 

 colour of the antennas and legs are alike. The female is similar in form to the 

 male, has the same alutaceous upper surface and paucity of pubescence as 

 my female nigrita, but is darker in colour, and has the punctures on the thorax 

 and elytra much finer. A long series, from various localities, may possibly show 

 this species to be only a form of my nigrita; my series (33 $ , 30 $), however, 

 does not enable me to unite them. I strongly suspect that H. brevis, Sahib., is 

 founded on a small female form of my nigrita, which has the apex of its elytra 

 somewhat prominent ; and if H. glabellus, Thorns., be another form of it, the 

 sculpture of the upper surface has been omitted, as it has been in the descriptions 

 of many other female Hydradephaga. 



H. honticola, Sharp. I have taken this insect both in Northumberland and 

 Cumberland, generally in mossy holes on the moors. Mistaking it for H. mela- 

 narius, Stu., I have sent it to some of my friends as such. It is, however, abun- 

 dantly distinct from that species. 



