THE CANAt)IA.N ENTOMOLOGIST. 181 



THE COLEOPTERA OF CANADA. 



B\' H. F. WICKHAM, IOWA CITY, IOWA. 



XL The Hydrophilid^ of Ontario and Quebec. 



These water-beetles differ from Dytiscid?e especially in having the 

 antenn;ie terminated by a distinct club instead of being filiform: and 

 while, as the name implies, they are usually found in ponds or streams, 

 they are much more feeble swimmers than the Dytiscids, and are 

 exponents of a more generalized type. Several genera are truly terrestrial 

 in habit, the beetles occurring about decomposing animal matter or in 

 manure. The larvae somewhat resemble those of the Dytiscida; in 

 general appearance, but differ so far as my experience goes in having 

 toothed mandibles instead of the single suctorial ones characteristic of 

 the other family. Pupation takes place on land in an underground cell, 

 or in a cavity scooped out beneath a stone or piece of wood. 



The generic table is based chiefly on the characters used in the 

 LeConte and Horn " Classification," and it is hoped will prove useful. 

 Care must be given the small specimens, and it will be found impracti- 

 cable to separate them without a good lens. The genera recorded in the 

 Canadian lists separate as follows : — 



A. Prothorax narrower than the elytra, and usually narrowed behind ; 

 form elongate, sculpture usually rough. 



b. Elytra with ten striae or rows of punctures, max. palpi moderate. 

 c. Last joint of max. palpi longer than preceding. 



Antennae 9-jointed Helophorus. 



Antennae 7-jointed HydrocJms. 



cc. Last joint of max. palpi shorter than preceding. . Ochthebius. 

 bb. Elytra with more than ten rows of punctures, maxillary palpi 



very long Hydrana. 



AA. Prothorax at base as wide as the elytra, narrowed anteriorly. Form 

 usually convex, oval or elliptical, sculpture usually weak, 

 d. Middle and hind tarsi with first joint short. 



e. Tarsi compressed, metasternum with distinct spine, 

 f. Prosternum sulcate, metasternal spine long. 



Large species (over i in. long), last joint of max. palpi 



shorter than the preceding Hydropltihis. 



Smaller species (less than yi in. long), last joint of 

 max. palpi equal to or longer than preced- 

 ing Tropisternus. 



ff. Prosternum carinate, metasternal spine short.. /T^'^/wZ/rtir/.s', 



