438 COLEOPTERA. 



seize their food by throwing their heads back and extending 

 the jaws. The larva of the European H. piceus Linn. (Fig. 

 382) matures in two months, then ascends to the bank, forms 

 an oval cocoon, and transforms to a beetle in about forty days. 

 In the genus Spercheus (S. tessellatus Mels.) the middle and 

 hind tarsal joints are equal in length. Hydropliilus is large, 

 oval, olive-black and with smooth elytra. In the larva the 

 lateral appendages of the abdomen are soft, flexible, ciliated, 

 and assist in buoying up the heavy, fleshy body (for which 

 purpose the antennae are ciliated) but they do not serve for 

 respiration as in Berosus, another extensive genus of this 

 family. (Schiodte.) H. triangularis Say is a large, pitch} r 

 black species. In Hydrobiu* the last joint of the maxillary 

 palpi is longer than the preceding. Spliceridium and its allies 

 are characterized by an ovate, convex or hemispherical form, 

 with ten rows of punctures or striae, though in Cyclonotum 

 there are no striae. In Cercyon the mesosternum is not pro- 

 duced, and the prosternum is keeled over. "In the larvae of 

 Cercyon and Sphceridium, which represent the Hydrophiline 

 type modified for life on dry land (though in humid places), 

 we find neither lateral abdominal appen- 

 dages, nor even true feet, the animal wrig- 

 gling its Way through the debris amongst 

 which it lives, whilst the last abdominal 

 segment is the largest of all and is often 

 armed with hooks." (Schiodte.) 



PLATTPSYLLID^: Leconte. The only spe- 

 cies of this family known is a small brown 

 insect, *16 inch long (Platypsytta castoris 

 Ritsema, Fig. 382 1 , enlarged), found on 

 the American beaver. The body is broad, Fi s- 3821 - 



flattened, eyeless, with short elytra, and spiny on the legs and 

 salient parts of the body, as in the flea. Leconte remarks that 

 its affinities are "very composite, but all in the direction of the 

 Adephagous and Clavicorn series, though chiefly with the latter.' 



SILPHID^E Leach. The Carrion or Sexton beetles are useful 

 in burying decaying bodies, in which they lay their eggs. 



