154 SELECTED NOTES FROM 



ZOOLOGICAL. 



Velia currens (PI. 15, upper half) is an Hemipterous insect 

 belonging to the family HydrometridcB. In the last week of 

 December I found a little swarm of about twenty or thirty strange, 

 spider-like insects darting forward by leaps upon the surface of 

 running water in a brook in this neighbourhood (Norwood), and 

 after some trouble succeeded in capturing one. On comparing it 

 with Westwood, and with Douglas and Scott's " Hemiptera- 

 Heteroptera," I find it agrees sufficiently with their account to 

 enable me to recognise it as Velia currens ; but there are some 

 points of difference in both descriptions which are worthy of 

 notice. Like the allied genus, Gerris, it is found under two 

 forms — a winged and an apterous condition : the one I found will 

 be seen to be the latter. It differs from Gei-ris most markedly in 

 the stouter and more oval form of the body, the comparative 

 shortness of the legs, and their more equable distribution — the 

 two posterior pairs of Gerris being placed close together, and at 

 some distance from the anterior pair. Westwood says of the 

 Hydro7netridcB^ that the antennae are four-jointed, the terminal 

 joints having occasionally a minute rudimental process at their 

 base. This would make them five-jointed, and therein Westwood's 

 statement agrees with that of Douglas and Scott, who describe 

 the genus Velia as five-jointed ; but if we include the rudimental 

 joints in the enumeration, I find that both Velia and Gerris 

 possess at least six joints, if not more, — as displayed in Figs. 2 

 and 6, PI. 15 ; where it will be observed that not only the terminal 

 joints, but the penultimate also, are furnished with this rudimental 

 one, thus making six. There is also a ball-like joint at the base of 

 the antennae, but I am not quite sure whether this is properly to be 

 reckoned amongst the components of the antennae, or whether it 

 is part of the face. 



Again : Westwood says of the family that " the tarsi are short 

 and two-jointed, occasionally, however, three-jointed, as in the 

 fore-tarsi of Velia,'' from which one might fairly infer that the 

 possession of three joints was confined to the fore-tarsi alone 

 of this insect, instead of which I find that all the tarsi are three- 

 jointed, as in Fig. 5 ; the basal joint being distinct although 

 minute, like the before-named rudimental joints of the antennae. 

 The ungues in this insect are inserted in a cleft in the terminal 

 joint, as in Fig. 4, beyond which they scarcely project. Douglas 

 and Scott say that the apterous form is common in small com- 

 panies on clear streams from March to September, but mine were 

 found at the latter end of December. 



A, Hammond. 



