British Species o/Haliplus. 115 



as sufficiently distinct to be called a variety, and my chief 

 reason for not separating it as a species is that in the form of 

 the aedeagus and its accessory lobes the two are identical. 

 Now all tlie other species of this group are to bedistinguisiied 

 on the aedeagal characters, and nomax and brow neanus awwxot 

 therefore be regvnrded as of the same standing towards one 

 another as either of them is to any of the other species. If 

 they are to be regarded as separate species, they must form a 

 distinct genus or subgenus apart from the others, and there 

 is not sufficient justification for this. 



H. nomax is, so far as is at present known, a northern and 

 western form occurring in the following counties and vice- 

 counties : — Ireland'. Antrim, Down, and Oarlow. Scotland: 

 Clyde Isles (Arran and Bute), ilsnirew, Lanark, Ayr, and 

 Kirkcudbright. England : I have seen a cJ of the species 

 from Ledsham, Cheshire, taken by W. E. Sharp, but that 

 was before " hroioneanus" had been separated, and I do not 

 know to which form it belonged. Otherwise there is, so far, 

 no English record for tlie type. 



It is a hike-species, found most abundantly in May and 

 June, but continuing to occur until August or even Sep- 

 tember, chiffly in the more stony parts. It, however, also 

 occurs — though never abundantly — in rivers and canals 

 where stony conditions may be absent, but where otherwise 

 some lake conditions exist, such as large volume of well- 

 oxygenated water and equable temperature. 



Tlie variety lias so far only occurred in Bucks and East 

 Anglia (Cambridge and Norfolk E.), where it seems to be 

 almost confined to rivers and broad drains of slow-moving 

 water, though I found it the dominant Haliplid in one or two 

 large and deep ponds in an old clay-pit near Cambridge. 



H. nomax varies somewhat in general form, usually being 

 widest a little behind the shoulders; but in some cases the 

 elytra are almost parallel for some distance back, while in 

 others the widest point is about halfway back. The var. 

 hrowiieanus is apparently less variable, the form being widest 

 a little behind the shoulders and more acute at the apex than 

 in normal nomax. The thorax is slightly longer in propor- 

 tion to its width, and tlie sides are less strongly convergent 

 anteriorly than in the type. The insect is ratlier smaller 

 tlian most nomax, and is rather more brightly coloured, 

 owing to the dark elytral lines being narrower and the 

 ground-colour pale yellow instead of testaceous. The usual 

 elytral marking both in nomax and the variety reminds one 

 oi fiuviatilis more than of any other species. 



In both the type and the variety the basal segment of the 



8* 



