222 HYDR0PHILID.I5. [Hydwhuna. 



ii. Veutrnl segments seven ; auterioi' coxal cavities closed 



behind ; elytra truncate LiMNEBlUS, Leach. 



II. First and second ventral segments covered by two plates 



meeting in middle Ch^taetheia, Steph, 



nVSROBZUS, Leach. 



The genus Hydrobius proper contains only a very few species, of 

 moderate size, and of a black or slightly l)ronzy colour ; they are found in 

 stagnant water, and are widely distributed over Europe, Asia, and North 

 America ; in a wider sense it comprises forty or fifty species, all occurring 

 in temperate regions and not entering the tropics. 



The larva of Hydrolkis fuscipes is figured by Schiodte (i., PI. iv., Fig. 5) : it is of 

 a dirty-white colour with the scuta fuscous ; it is broadest in the middle and much 

 narrowed in front and behind; the head is very small with exceedingly short antennae, 

 the prothorax quadrate, much narrower than the following segments, with the scutum 

 entire; the scuta of the meso- and meta-thorax are incomplete, and those of the 

 abdominal dorsal segments are broken up and take the form of minute warty corneous 

 plates, four on each segment ; the segments tliemselves are much wrinkled in transverse 

 folds ; the eighth segment is very much narrowed, and bears two almost imperceptible 

 cerci and a very small prominence at apex ; the legs are very short. 



The larva of Philhydrus and the allied species bear so close a resemblance to that of 

 Ht/drobius that they hardly require a separate description ; that of P. testaceus is 

 figured by Schiodte (i., PI. iv., Fig. 6), and a reference to his plate will show their 

 extreme similarity ; the female beetles diifer from the female of Helochares (the larva 

 of which is very closely allied to that of these species) in not caiTying their eggs in a 

 sac attached to the abdomen. 



1. Elytra with distinct punctured striaj, strife deep towards 



apex ; length 5-7^ mm H. FUSCIPES, L. 



2. Elytra with fine rows of punctures, not striated ; length 



8-9 mm H. oblongtjs, Herhst. 



K. fuscipes, L. Oval, convex, black or pitchy black, shining, 

 female duller than male ; thorax much broader than long, very closely, 

 but distinctly, punctured ; elytra as broad at base as base of thorax, .with 

 eleven punctured strise on each ; interstices closely punctured, the alternate 

 ones furnished with a row of pores ; legs ferruginous, femora darker at 

 base, posterior femora pubescent almost to apex. L. 5-7| mm. 



Common and widely distributed throughout the kingdom. 



H. picicrus. Sharp, appears to be a distinct race of this species, and 

 may perhaps be considered distinct : it differs from the type form in 

 being rather smaller, shorter, and more convex ; the tibiae as well as the 

 extremity of the femora are pitchy, and the hind angles of the thorax 

 form a more obtuse right angle ; the striae of the elytra also are more 

 strongly punctured ; it has been found in the following localities : Ask- 

 ham Bog, York ; Liverpool ; Knowle, near Birmingham ; Wicken Fen ; 

 Lymington ; Corstorphine Hills, Scotland, &c. 



A variety very rarely occurs in which the upper surface is of a strongly 

 metallic greenish or bluish colour. 



K. oblong-US, Herbst. {piripes, Fab.). Very like the preceding, but 



