DYTISCLD.E. 



63 



I. Dytisci fragmentati. 



i. Greatest anterior extension of the hind coxa near 



the middle (longitudinally) of the body ; 

 metasternum more or less'pointed in the middle 

 behind, and not marked by a transverse 

 suture 



ii. Greatest anterior extension of the hind coxa 



nearer to the epipleura than to the medial line 

 of the body. 



1. Prosternal process not reaching the meta- 



sternum 



2. Prosternal process reaching the metasternum . 



II. Di/tisci complicati. 



i. Presternum deflected between the front coxa? so 

 that the prosternal process is placed on a quite 

 different plane of direction from that of the 

 presternum ; the latter not incrassate along- 

 middle ; front tarsi usually 4- jointed. 

 1. Prosternal process much deflected from the 

 plane of direction of the presternum. Front 



tarsi usually with only four joints Hydroporin^e. 



2. Prosternal process but little deflected from 

 the plane of direction of the presternum ; 



front tarsi 5-jointed ; scutellum not visible . Methliis^e. 



ii. Prosternal process on the same plane of direction 

 as the presternum ; front tarsi 5-jointed. 

 1. Inferior spur of hind tibia not or but little 

 broader than the other. 

 A. Hind margins of joints of posterior tarsi not 

 set with flattened and adpressed cilia. 

 a. Stigmata of last two dorsal segments not, 

 or but little, broader than the preceding 



ones ; outline of eye notched by the free 



margin of front of head CoLYMBETiNiE. 



b. Stigmata of the last two dorsal segments 

 enlarged, each on the penultimate 

 segment being about one-fourth, of the 

 total breadth of the segment ; circular 



outline of the eye uninterrupted Dytiscinje. 



13. Hind margins of joints of posterior tarsi 

 provided externally with flattened 



adpressed cilia IIydaticen^e. 



2. Inferior spur of the hind tibia dilated, much 



broader than the other Cybistrip<le. 



The Vatellin^e are small insects with somewhat of the outline 

 of Amphizoa, the swimming legs being very slender and not dilated ; 

 the three genera are all from South or Central America. The 

 subfamily Metiili^^e consists only of three species from Tropical 

 Africa, Madagascar, Mesopotamia, and Egypt ; they are of the 

 shape of small Hijdropori, with the swimming legs very feeble and 

 the extremity of the body acuminate or spinose. The other 

 divisions are well known. The characters of the divisions are in 

 some eases rather intricate, but they will be found workable ; the 



NOTERINiE. 



Vatellin.e. 



LACCOPHILINiE. 



