Ili/dncna.] hydhophiliu.e. 251 



colour ; the latter species cannot be confused witli any other except light 

 specimens of atricajjilla, from which it may at once be separated by the 

 rounded apex of its elytra, and different sculpture. 



It is worthy of note that only two species of Ht/drcena (II. fesfacea 

 and JI. riparia) appear to occur in the London district, and only two 

 or three species are found in the south of England, whereas all the 

 ]>ritisli species, with the exception of //. palustris, are found in the 

 Northumberland district, and in Scotland ; this is the more strange as 

 seyeral of our rarer northermspecies (//. an'/ustafa, pi/f/tmna, pulchdld, &c.) 

 are found in France, and there is no reason why we should not find them 

 widely distriluited in England; it is quite possible that owing to their 

 rarity and tlieir minute size they have been passed over by collectors. 



SPHiERIDIIN^. 



The second sub-family of the llydrophilidaj, the Si)hairidiina3, appear 

 both by their structure and habits to form the connecting link between 

 the lIydrophilida3 and the Silphida? ; they are, as a rule, teritjstrial in 

 their habits, and were accordingly named Geophilides by Mulsant, as 

 opposed to his other division Hydrophilides ; several species, however, 

 are subaquatic, being found in damp places, in moss by the side of jionds 

 and streams, or even in the water ; they feed on decaying vegetable 

 matter, and may 'be found in great numbers in dung, especially that of 

 herbivorous animals ; the species of the large genus Cercyon, in spite of 

 their minute size, by reason of their countless numbers form one of our 

 inost useful scavenging agencies, and in conjunction with the Aphodii, 

 fleotruiies, and other Xecrophaga, do the greatest service in })artly clear- 

 ing oil' the dung through its consumption by their larvic, partly in riddliu"- 

 it through and through with holes and galleries so that the rain is able 

 freely to percolate through it and wash it into the ground. 



The Sph3eridiina3 are, as their name implies, round, convex, sometimes 

 almost lu^mispherical insects ; they are sometimes fully striated, some- 

 times smooth except for a sutural stria ; the maxillary palpi are not so 

 strongly developed as in many of the Hydrophilid;e, but they are often 

 as long as or slightly longer than the antenniE ; the onychium or last 

 joint of the anterior tarsi is very long, as long as or longer than the four 

 others united, and is often considerably dilated in the males; the first 

 joint als(j of the posterior tarsi is elongate, a character which at once 

 separates the family from the Hydropbilid;v, in which the tirst joint is 

 very short and often hidden so that the tarsi ap[)far tctramerous ; the 

 tibiie arc spinose and adapted for digging ; good generic characters are 

 found in the shape of the scutellum, and also in the form of the nieta- 

 sternum, which as a rule is much longer than broad, but in Ma/a- 

 sfpimnii and Cnjptopleurum is very broad, the breadth exceeding the 



Irl.gUl. 



The liirvfc of this family arc destitute or virtually (Uvtitiite of legs, and in this 

 difl'er widely from those of the Ilydroiihiliuiu, which are furnished with disliuct legs 



