254 HYDROPHiLiDiE. [Cerrijnn. 



species, which are widely distributed over the surface of the globe ; 

 many of them are very difficult to determine, as may be gathered from 

 the fact that Stephens described no less than sixty species from Britain 

 alone ; the majority of the species live in the excrement of herbivorous 

 animals, but some are only found in moss, &c., on the margins of ponds 

 or streams, while a few live under sea-weed and decaying vegetable 

 matter on the sea coast in localities that are often submerged at high 

 water ; they are all small, but vary considerably in size, and also in 

 colour ; the chief points of distinction lie in the size, shape, and punc- 

 tuation of the interstices of elytra ; in many cases the colour is a sure 

 means of distinction, but occasionally it is misleading : the larva of C. 

 littorale is described by Thomson (Skand. Col. ii. pp. 103, 104); it is 

 pale testaceous, with the head ovate, the prothorax semicircular, and the 

 mesothorax transverse ; the maxillae are longer than the antenna3, which 

 are three-jointed ; the mandibles are sickle-shaped, sharp at the apex, 

 with a sharp tooth on their inner margin ; the abdomen is coriaceous 

 with the last ventral segment tricuspid ; there are no legs ; it is found 

 under sea- weed with the perfect insect. 



The larva and pupa of Cercyon analis are fifrurerl hj- Scliiiidte (i., PI. vi., Figr. 8 and 

 24) : tlie lavva very closely resembles that of Spharidium scarahcfoides, but the scuta 

 of the meso- and meta-thorax are incomplete, and the eighth sea-ment bears two short 

 filamentous cerei and no conical appendages ; the legs are entirely wanting : the pupa 

 of Cercyon is narrower and not so round as that of Splxeridium ; it is not so thickly 

 coveVed with the long appendages so marked in the pupae of the Hydrophilida;, and 

 called by Schiodte the " styli motorii," and the cerei attached to the last segment are 

 longer. 



I. Upper surface depressed (species always found on the 



coa>t). 



i. Anterior tibiae emarginate at apex ; striae of elytra 



continued to apex < . . . C. littoralis, Oyll. 



ii. Anterior tibiae simple at apex ; striae of elytra obso- 

 lete towards apes C. DEPRESSUS, Steph. 



II. Upper surface more or less convex (species generally 

 distributed). 



i. Thorax separately convex, forming an angle, when 



viewed sideways, with the convexity of the elytra . . C. iijemotlrhovs, Gyll. 

 ii. Thorax and elytra, viewed sideways, presenting an 

 evenly rounded contour. 



1. Punctuation of interstices of elytra distinct. 



A. Length 3-4 mm. 



a. Elytra slightly narrowed towards apex ; 

 fourth stria of elytra parallel to third ; size 



smaller C. H.KiroRRHoiDALis, F. 



b. Elytra as broad in front as behind ; fourth 



stria of elytra approaching third ; size larger C. obsoletus, Gyll. 



B. Length 2-3 mm. 



a. Sides of thorax concolorous with disc ; apex 



of elytra often prolonged into a tooth, 

 a*. Elytra lighter or darker reddish brown . C. flaVIPES, F. 

 b*. Elytra orange red with a well-marked 



triangular dark patch around scutellum . . C. melaXOCEPHAltts, L. 



b. Sides of thorax more or less broadly reddish or 

 yellowish ; apex of elytra not prolonged. 



