542 CLASS vin. 



First joint of tarsi very short, strictly connate with second, last 

 elongate. Antennae with seven to nine joints. Body oblong. Thorax 

 narrowed towards the base. 



Sub-genera : Hydrwna, Kua, Ochthebius LEACH, Uydroclius 

 GERMAR, Helophorus ILLIG. 



Sp. Heloph. grandis ILLIG., Eloph. aqiiaticus FABR., DUMERIL Cons. gen. s. I. 

 Ins. PI. 6, fig. 8, STURM Deutschl. Faun., Ins. x. Tab. 219, fig. A &c. 



Spercheus FABR. Maxilla with external lacinia horny, palpi- 

 form, acuminate, incurved, ciliated internally, with internal lacinia 

 coriaceous, pilose at the apex. First joint of tarsi not less than 

 second, last elongate, equalling the first four in length. Antennas 

 short, thick, sex-articulate. 



Sp. Spercheus emarginatus FABR., PANZER Deutschl. Ins. Heft 91, Tab. 4, 

 STURM 1. 1. ix. Tab. 214, Cuv. R. Ani. ed. ill., Ins. PI. 38, fig. 4; 3'" 

 long, dull brown, very convex on the back ; head-shield excised in front : 

 this little beetle creeps upon the roots of water-plants. 



This genus forms the transition to the following family, and from the form 

 of the under-jaws belongs to the neighbourhood of Gyrinus. 



Family LXII. Hydrocantharina or Dytiscina. Maxillae homy, 

 with external lacinia palpiform, articulate. Mandibles, as to the 

 greatest part, covered. Four posterior feet natatory, two posterior 

 remote from the rest. Body oval , thorax broad, transverse. 

 A. Abdomen composed of six segments. 



Gyrinus GEOFFR., L. Antennas shorter than head, fusiform, 

 with nine joints, auriculate at the base. Eyes divided by the 

 lateral margin of head into two parts quite separate. Anterior 

 feet long, porrect ; four posterior feet short, broad. Elytra poste- 

 riorly rotundate, not covering the apex of abdomen. 



Sub-genera : Orectochilus ESCHSCH., Cylister ESCHSCH. (Gyretes 

 BRULLE), Dineutes MAC L. (Cyclous ESCHSCH., DEJ.), Gyrinus, En- 

 hydrus LAPORTE. Comp. AUDOUIN et BRULLE Hist. nat. des Ins. v. 

 pp. 234242. 



Sp. Gyrinus natator L., E(ESEL Ins. in. Tab. xxxi., PANZER Deutschl. Ins. 

 Heft 3, Tab. 5, AHRENS et GERMAR faun. Ins. Europ. n. Tab. 5 ; the 

 male 2'", the female 3'" long, blue-black, shining ; the shields are stippled 

 in longitudinal rows. These whirling beetles make their appearance early in 

 spring in fresh water, revolving in circles on the surface of the water with 

 much rapidity. On the least alarm they dive suddenly below. Several other 

 European species are figured in AHRENS and GERMAR Faun. Ins. Eur. 

 Tab. II. 



