120 SUBDIVISION OF BEETLE TRIBE. 



are destitute of members. The larvae of the carnivorous 

 species have in general the most robust legs ; and in some of 

 the herbivorous species these are assisted by fleshy tubercles, or 

 pro-legs. A pair of these frequently exists on the last segment 

 of the abdomen. Previously to undergoing its change, the larva 

 often forms a case for itself, of bits of earth, or chips of wood, 

 united by silken threads, or by gluey matter. The pupa, or 

 chrysalis, is inactive, sometimes even for years, and takes no 

 nourishment ; but the form of the future Beetle is plainly 

 perceived, the different parts being encased in distinct sheaths. 

 (Fig. 435). 



700. There is much difficulty in forming a simple natural 

 classification of this immense tribe, on account of the great num- 

 ber of distinct species which it includes, and their strong general 

 resemblance to each other. Hence it is often necessary to resort 

 to characters of great minuteness as the ground-work of the 

 system ; and it sometimes happens that, by the adoption of such 

 a plan, tribes which are in reality closely allied in general struc- ' 

 ture, are placed in different groups, whilst others are brought 

 together which are in many respects dissimilar. The system 

 here followed is founded upon that proposed by Latreille ; who 

 took as the basis of his classification the number of joints in the 

 tarsus or last portion of the foot ( 664). The four following 

 sections are thus formed. 



I. PENTAMERA (five-parted), in which the tarsi of all the feet 

 are distinctly 5 -jointed. 



II. HETEROMERA (differently-parted), in which the tarsi of 

 the first two pairs of feet are 5 -jointed, and the two posterior 

 4-jointed. 



III. TETRAMERA (four-parted), in which all the tarsi appear 

 to be 4-jointed. (The fifth joint exists in these, although it is 

 very minute, and concealed in one of the others.) 



IV. TRIMERA (three-parted), in which all the tarsi have three 

 distinct joints. (A fourth of small size is also present.) 



Each of these sections contains several families ; of which the 

 most important will now be noticed. It must be borne in mind, 

 that the characters drawn from the number of joints in the tarsi, 



