544 CLASS vni. 



B. All the tarsi with five joints. First three joints of anterior tarsi in 

 males broad, transverse. 



Colymbetes CLAIRV. Scutellum conspicuous. (Sub-genera : Colytn- 



betes, Hybius ERICHS., Agabus LEACH, ERICHS.) 



t 

 Sp. Dyt. fuscus L., PANZER Deutschl. Ins. Heft 86, Tab. 5, CLAIRVILLE 



Entom. helvet. n. PI. 29, fig. B, &c. 



Laccophilus LEACH. Scutellum covered. Antennae thin, seta- 

 ceous. 



Sp. Dyt. hyalinus DE GEER, Laccophilus minutus STURM, Dyt. obscurus, 

 PANZER Deutschl. Ins. Heft 26, Tab. 3, &c. 



Noterus CLAIRV. Scutellum covered. Antennae incrassated in the 

 middle (especially in males). 



Sp. Dyt. crassicornis FABR., &c. 



C. Anterior tarsi in both sexes subequal. (First and second pairs of 

 feet with tarsi of four joints, the penultimate joint obsolete or concealed.) 



Hyphydrus (!LLIG., GYLLENH. Sp. of Hydrachna FABR.), Hydro- 

 porus CLAIRV. 



Sp. Dytisc. palustris L., Dyt. lituratus PANZER Deutschl. Ins. Heft 14, Tab. 4; 

 Dyt. rufifrons DUFTSCHM., STURM 1. 1. ix. Tab. 207, fig. A, &c. 



Pelobius SCHOENH., ERICHS. (Species of Hydrachna FABR., 

 HygroMa LATR.) Antennas filiform, short, with eleven joints. 

 Head sub-exsert, with eyes somewhat prominent. Labrum emar- 

 ginate. Thorax very short, much broader than head. Posterior 

 coxae narrow. Tarsi all with five joints, slender. Scutellum 

 distinct. 



Sp. Pelobius Hermanni, Hydrachna Hermanni FABR., PANZER Deutschl. Ins. 

 Heft 10 1, Tab. i, STURM 1. 1. vm, Tab. 200. 



Haliplus LATR. Antennae scarcely longer than head, filiform, 

 thin, with ten joints. Labrum entire, with margin ciliated. Pos- 

 terior coxae narrow, covered by an orbicular plate. All the tarsi 

 with five joints. (External maxillary palps with last joint narrow, 

 subulate). 



Sp. Haliplus ruficottis, Dyt. ruficollis, DE GEER Ins. iv. Tab. 16, fig. 9, 

 PANZER Deutschl. Ins. Heft 14, fig. 10. 



Cnemidotus ILLIG., ERICHS. 



Note. Differs from Haliplus in the last joint of external maxillary palps 

 being greater, conical. Sp. Haliplus ccesus GYLLENH., PANZER Deutschl. 

 Ins. Heft 14, Tab. 7, D^JEAN et AUB, Iconogr. v. PI. 3, fig. 2. 



