British Species of ^ii\i^\\xs. 113 



I expect that it is. more widely distributed than the records 

 indicate. The only Irish locality is in (;0. Down, where it 

 occurs fairly connnonly in pools on the salt-marsh nt Killough. 

 The only Scottish records are for Dumfries and Kirkcudbright, 

 while tlie English records are for Durham, Yorks N.E., 

 Norfolk E., fciuifolk E., Kent W., and Hants S., and 

 Warwick, wdiere it is described as being- '' local and rare at 

 Knowle," probably erroneously (6). 



With regard to the characters for determining the species, 

 I have drawn up a short summary, which may be useful, 

 althouohj as 1 have already said, the species are very difficult 

 to distinguish except by examining the male armature. 



General Summary of Characters. — 



fl. General form long and rather parallel-sided. 



2. Thorax not more than twice a3 broad as lon^ ; the sides practi- 

 cally sti-aight. 



3. Thoracic stria) long and straight. 



A,<( 4. EljHra with the black lines usually not spreading into patches ; 



I lines not usually broken, 



5. Prosternum flat, with a tendency to be slightly concave ;' some- 

 what dull in appearance, owing to closely-set fine punctura- 

 1^ tion umid scattered large punctures. 



) 1. Ant. tarsal claws almost eaual in length. 

 ) 2. Basal segment of median tarsus not excised on posterior side, 

 ^ . 1. Elytra covered with fine puncturation. 



<S 



With regard to aideagal characters, the figures show all 

 that is necessary. Note the narrow triangular form of the 

 left accessory lobe, with its dorsal edge sligiitly concave and 

 fringed with a row of fine stiff hairs, which row extends to 

 the blunt ajDex and ends in a small tuft. Edwards wrongly 

 describes and draws this lobe as without the hairs. The 

 side of the tongue shows a thin chitinous patch slightly 

 creased longitudinally. Possibly this is of similar use to the 

 more elaborate saccular region of the more complex types. 



2. H.fiuviatiUs, Aub^. 



This species is almost confined to running water, and is, in 

 fact, the most typically " river species " of the " rujicollis" 

 group. It is superficially, perhaps, the most easily distin- 

 guished species, which, however, is not saying very much. 

 It is fairly widely distributed throughout the Britannic area, 

 and also on the continent, and, as we have seen, the female 

 shows variations with regard to the fine puncturation of the 

 elytra. The species is recorded from most parts of Ireland 

 and England, but there is, so far, no Welsh record, and it 

 seems to be absent from Scotland north of Stirling. I failed 



Ann. & Mag. N, Hist. Ser. 8. Vol xv. 8 



