60 INTRODUCTION. 



[Family 4. HYGKOBIID^ (or PELOBIIME).] 



Head not sunk in prothorax ; antennas inserted at the side margins 

 of the forehead, eleven-jointed, without pubescence ; metasternum with 

 a very short ante-coxal piece, the suture indistinct ; anterior coerce 

 conical ; rnetasternal episterna not reaching the middle coxed cavity ; 

 h ind legs slender, but formed for swimming, with the tarsi longer than 

 the tibial, and all the tarsi and tibice rather thickly set with swim- 

 ming hairs; elytra with a str ululating file on their inner side at 

 apex. 



This family is in several ways rather nearly related to the 

 Ampiiizoid^e and like the latter family is closely allied to the 

 Caiiabiile ; it differs from the first-mentioned family in being 

 specially adapted for swimming, and, according to Sharp, it may 

 be described as a Carabid adapted to a considerable extent for 

 swimming in water. In his great work on the Dytiscid.e (Trans, 

 Royal Dublin Soc. vol. ii, series 2, p. 255), Sharp classes the 

 Pelobiid.e with his Dytisci fragmentati, but in his later work he 

 regards them as a separate family between AMPiiizoiniE and 

 Haliplio.e. 



The larva of Pelobius is very curious, its general appearance 

 being crustacean rather than coleopterous. The head is broad 

 and almost semicircular, the prothorax very large and trapezoidal ; 

 the scuta cover the whole upper surface of the segments; the 

 last abdominal segment bears three long setose cerci, and the small 

 anal process is retracted between them. Dr. Sharp's statement 

 that there are three cerci is probably right ; in my description of 

 the larva (Col. Brit. Islands, i, p. 158), I have treated the third 

 cercus as being the anal appendage, but it is apparently a some- 

 what abnormal cerens. The larva is furnished with branchiae or 

 gills on its under surface: it lives in water and is very predaceous. 



The distribution of Pelobius is as strange as that of Amphizoa. 

 When I wrote my book on British Coleoptera only three species 

 were known, one from Europe, and the other two from Australia; 

 since then a third has been added, from Chinese Tibet ; repre- 

 sentatives may very likely be found in Northern or Southern 

 India. 



