102 PARTIAL ORISMOLOGY. 



observe among some of the Ichneumons (Icli. melanogonus, Grav. ; 

 Pimpla mesocentra, Grav.) 



IV. The fourth joint of the leg is the SHIN (tibia, PI. XVI. f. 1, rf.) 

 But in the same way as the thigh is united to the hip through the 

 medium of the trochanter, so is the shin connected with the thigh, viz. by 

 ginglymus, but in a reversed direction, for whilst in the former articu- 

 lation the shanks are directed upwards, in the latter it is the apex. 

 With respect to its form, it is very generally as long as the thigh, and 

 it is equally often thinner and more slightly framed. Notwithstanding 

 which, we observe more differences in the tibia than in the thigh ; it is 

 found conical, tubular, triangular, quadrangular, compressed either 

 partially or entirely, leaf-shaped, uneven and rough. It is not unfre- 

 quently that we perceive them armed or clothed with spines, either 

 solitary or placed in rows, with very long hair, teeth, fringe (tib. 

 Jimbriatce), and setae. Indeed they occur more frequently upon the 

 shank than upon the thigh. In form, however, it is very much 

 regulated by that of the thigh, and its structure appears to agree as 

 intimately as is compatible with the preformed figure of that joint. 

 For example, should the thigh be conical, the shank forms a bow, 

 which fits closely to the cone (Chalets'), or if the thigh be convex, the 

 shank then forms a corresponding inflection. The same is the case in 

 raptorious legs (Mantis). At the end of the shin, and around the 

 cavities, wherein the following joint articulates, in general we observe 

 some spines, which are usually called SPURS or TERMINAL SPINES 

 (Calcaria, Spicula, PL XVI. f. 1. 8, 8.) They are indeed most fre- 

 quently mere processes of the horny substance, but they are sometimes 

 articulated, and have a free motion at the will of the insect (Mantis'). 

 In this case they form a species of pincers (Hylobius Abietis), which 

 assists the insect in climbing. 



V. It is to the shin that the last division of the leg, the FOOT (tarsus, 

 PI. XVI. f. 1, <?.) is attached. It consists of a series of consecutive 

 joints, the first of which is generally the largest, and the following 

 gradually decrease until the last, which is again longer than the one by 

 which it is preceded. The last is armed with claws and appendages at 

 its termination. The connection of the first with the shin is also by 

 ginglymus, and indeed the fork of its two shanks point upwards, 

 whereas the joints of the foot itself are connected so together that they 

 form but one surface in their union. The cavity of each joint is placed 

 near the upper surface, often in its very centre, and its anterior margin 

 is produced beyond it. By means of this arrangement, the joints 



