218 iiYDROPniLiD.1:. \_Hij(lrophiUdx. 



dung of herbivorous animals, &c. ; the term Palpicornia is perhaps more 

 suitable for the group than the names Hydrophilidfc or Philhydrida by 

 which it is usually known, the chief distinguishing mark being the 

 development of the maxillary palpi ; these in many instances are several 

 times longer than the antennae, which are very short in the majority of 

 the Hydrophilinae ; in the Sphaeridiinae the disproportion is not so 

 marked ; as, however, the family cannot be separated from the Clavicoruia, 

 the term Palpicornia causes confusion. 



It is a curious fact that the larvae of the Hydrophilinse, at all events as a general rule, 

 are carnivorous and eminently predaceous, even devouring one another, if other animal 

 food fails them, as I have observed in the case of the larvfe of Spercheus ; they form, 

 therefore, a rather strong connecting link between the carnivorous Coleoptera and the 

 purely vegetable feeders ; the Hydrophilidaj as a rule, with the exception of the Helo- 

 phorina and their allies, are of an oval convex form, sometimes hemispherical, and 

 often very shining ; the elytra are sometimes striate, sometimes possess only a sutural 

 stria, and occasionally this too is wanting ; in the species with smooth elytra there 

 are generally three irregular rows of punctures on each elytron as in the Dytiscidaj ; 

 the palpi are four-jointed, the antennae are made up (perhaps only apparently) of not 

 more than from six to nine joints, and terminate, as a rule, in a three-jointed club ; 

 the number of free ventral segments of the abdomen varies from five to seven ; the 

 tarsi are all five-jointed (except in the genera Hijdrocotnhiis and Cymhiodyta, in which 

 the middle and hinder tarsi are truly four -jointed), with claws furnished with a small 

 basal tooth : the relative difference in the length of the tarsal joints affords a valuable 

 character for the separation of the tribes ; this character, however, as used in separating 

 the two sub-families SydrophilincB and Spceridiinee is quite untenable if applied to the 

 exotic species ; in our limited fauna it holds good. 



The Hydrophilidae, as remarked by Dr. Sharp (Biol. Cent. Am. 

 Hydrophilidae, p. 53), will probably become a family of even greater 

 extent and importance than the Dytiscidse ; for the last-named family is 

 rich in species in the more frigid portions of the earth's surface, while 

 this is not the case with the Hydrophilidae, whose species appear to be 

 most numerous in the warmer regions, and as yet are very imperfectly 

 known in comparison with the more northern Dytiscidae. 



The connection of the family with the Dytiscidae is very superficial ; it 

 bears, however, strong relations towards other families of the Clavicoruia ; 

 through Hijdrochus it is connected with the Elmides, through Cercyon 

 Avith Anisotoma, and through Cryptopleurum with Ahrceus and the 

 Histeridce ; in the present state of our knowledge the best position that 

 can be assigned to it is perhaps between the Adephaga and the Silphida). 

 The two sub-families may be thus distinguished: — 



1. Legs provided with swimming cilia ; posterior tarsi with the 



first joint very short, often not visible from above IlTDROPHiLiN.Ti:. 



2. Legs not provided with cilia ; tibiae spinose ; posterior tarsi 



with the first joint elongate Sph^eidiin/E. 



Sub-Fam. KVDROPHII.INS:. 



Besides the above-mentioned characteristics, the members of this sub- 

 family have the labrum almost always very distinct and not hidden 

 behind the clypeus ; the larva) are always provided with legs, which are 



