1914.] 137 



informs me that it inhabits rocky pools in company with Deronectes 

 griseostriatus, and this quite agrees with my recollection of the spot 

 where I found G. opacus at Braemar. 



10. Gr. MARINUS Gyll. 



In this species there is a marked distinction between the sexes in 

 the sculpture of the elytra. Before attempting to study this insect it 

 is therefore desirable to separate the sexes. The male is smaller than 

 the female, often not more than half the size ; it is more shining, and 

 when examined with a magnifying power of about 60, is seen to have 

 on the elytra a very fine, scanty general punctuation ; in the female 

 this punctuation is vastly more dense and distinct, and some of the 

 punctures are a little extended so as to become very short scratches ; 

 hence the comparatively greater dullness of this sex. There is a little 

 variation in the sculpture, but not much, and this common species can 

 always be identified by the male sedeagus, which has invariably a long, 

 slender, pointed extremity (figs. 10), and the female sexual sculpture. 



11. (jr. EDWAEDSI, UOlll. UOV. 



G. opacus Suffrian, Sharp, Edwards et auctt. plurr., nee Sahlberg. 

 In this species the individuals are smaller than in marinus ; but 

 as in both the male is considerably smaller than the female, it is 

 necessary to separate the sexes before comparing the two insects. 



In the male of edivardsi the sedeagus (figs. 1 1) has the apical part 

 parallel-sided, and though slender, always truncate at the extremitv ; 

 and when carefully compared it is found that the shape is in otl 

 respects different in the two species, and there is no doubt as to t 

 distinction of the two. 



The female of edwardsi is smaller than that of marinus and is a, 

 little different in shape ; it also has the serial punctures of the elytra 

 smaller; but these differences are only slight, and one meets with 

 specimens of this sex as to which I find it impossible to decide with 

 full confidence. Fig. 13 represents the styles of this sex. 



This is the opacus of our collections in Britain. The species has 

 been believed by modern European authors to be the same as marinus, 

 and it has altogether disappeared from the European catalogue. There 

 is no doubt, however, as to its complete distinction from marinus, 

 although the two are frequently found in intimate association, and 

 although on cursory examination there appear to be numerous " inter- 

 mediates." This has been stated by Priederichs in Allg. Zeitschr. Ent., 

 viii, p. 260, who is inclined to speak contemptuously of those who 



