266 



NATURAL ARRANGEMENT OF INSECTS. 



elongate and depressed ; and each segment, beyond the 

 three thoracic ones which bear the slender legs, is fur- 

 nished laterally with an elongate,, inarticulated, ciliated fila- 

 ment; and the thirteenth with four articulated,, very pilose 

 appendages, of about the same length as the lateral fila- 

 ments. When it has acquired its perfect size,, this 

 larva creeps up some aquatic plant,, where it spins a 

 cocoon wherein it undergoes its transformation; thus,, 

 also differing from the Dytiscince, which undergo theirs 

 beneath the earth, and do not spin a cocoon. Of the 

 many water beetles collected by Mr. Darwin during his 

 voyage with the Beagle, the majority were minute and 

 well known forms resembling those occurring in our 

 own country. 



(235.) Being uncertain whether the SilphidtB orPime- 

 lidcK should occupy the situation of our fourth family, 

 we will give a brief description of the most remarkable 

 contents of each. The relation between the Dytiscida 

 and them, it is at present impossible to trace without 

 straining affinities ; and the Silphidce, in particular, of 

 which we will first treat, are considerably different, both 

 in habits and structure, from all that have preceded 

 them in this circle ; although connected, by means of 

 both, with the Staphylinidce. Their antennae are clavate, 

 the club being perfoliated ; their elytra usually abbre- 

 viated ; and in the aberrant forms of the family, there 

 is much divarication, and even sexual disparity, in the 

 number of the joints of the tarsi, although, typically, 

 they are pentamerous. The chief types, consisting of 

 the genera Necrophagus, JVecrodes, and Silpha, and feed- 

 ing as they do upon carrion, are, like the vulture, endowed 

 with the sense of winding it from afar; and upon a bright 

 spring day they will come soaring along, sweeping with 

 the velocity of a bee around the object of their solicitude, 

 and fall directly upon it. The species of Necrophagm 

 are called burying beetles, from the habit they have of 

 associating together for the purpose of excavating the 

 earth from beneath the dead animal (if not too bulky) 

 with which they are engaged, which sinks gradually 



