151 



A GUIDE TO THE STUDY OF BRITISH WATERBUGS 

 (AQUATIC RHYNCHOTA). 



By G. W. Kirkaldy. 

 (Continued from p. 115.) 



Velia, Latreille, is closely allied to the preceding genus. 

 There is a single British species, usually known as V. currens 

 (Fabr.) ; as, however, I am unable to distinguish it structurally 

 from V. rivulorum (Fabr.), and as no structural differences have, 

 to my knowledge, been mentioned by earlier authors, I record it 

 here as V. rivulorum (Fabr.). It has also been described under 

 the names affinis, aquatica, aptera, impennis, major, and ventralis ! 

 It is dimorphic, the head and thorax of each form being por- 

 trayed on PL 1, figs. 1 and 2. The anterior tarsus is shown on 

 fig. 4 (compare with that of Hydrometra, f. 5), and the sterna on 

 fig. 3 (compare with the sterna of Gerris, f. 11). The apical 

 segments of the venter, in the male, are delineated on fig. 14 ; 

 in the female they are not very dissimilar from those of the same 

 sex of Hydroessa, except that apical margin of the connexivum of 

 the 6th segment is produced acutely as in the male. 



Velia progresses in a very similar manner to Hydroessa ; 

 Meinert states* that it also readily moves beneath the surface of 

 the water, in the usual position and also back downwards. It is 

 then encased in a silvery air-bubble, and has very much the 

 appearance of the water-spider [Argyroneta aquatica (Linn.)]. 



Velia rivulorum chooses habitats of a very diversified nature : 

 streams — swift-flowing or slow — seem to form its usual haunts ; 

 but it may be found almost everywhere that fresh water occurs — 

 in the swirling pools at the foot of rushing cascades, on stagnant 

 meres, in solitary rock-pools left by the summer contraction of 

 mountain torrents, under stones at (and indeed some little dis- 

 tance from) the margins of lochs and ponds. As has been 

 previously remarked, many of the Gerridse conceal themselves — 

 in fact, "hybernate" — under moss, stones, &c, often far from 

 water, during the winter. I do not think this has been noticed 

 in the present species ; in fact, Fallen recordst its occurrence in 

 some numbers (in the apterous form), running about quickly on 

 the water, at a time when snow was lying on the frozen earth. 

 Of course they may, as a rule, hybernate like their allies. 



In the British Isles the apterous form is exceedingly common, 

 and well distributed from the Shetland Isles to the southernmost 



■•' " Vandl0berne, Hydrornetridae, deres Fserden og Leven" (in Entom. 

 Medd. i. p. 95, 1887), a valuable paper, to which I will refer later at some 

 length. 



f Hemipt. Svec. 1829, p. 161 ; o see also Meinert, I.e. p. 9G, and Eeuter, 

 1888, Ent. Medd. i. pp. 123-4, "Nagra ord orn Hydrometridernas ofver- 

 vintring." 



