THE THORAX. 101 



thorax, to which it is affixed by a single small spot (many Coleoptera) ; 

 and sometimes, lastly, it displays itself more flattened, in which case 

 it is affixed to the thorax by a firmer and closer union, which admits 

 of no free motion (for example, the posterior coxae of Dyticus, llu- 

 prestis, &c.). In this last case, frequently also in the first, the 

 coxae appear to belong more strictly to the thorax than to the legs, as 

 they stand in much more intimate connection with the former than with 

 the latter ; but their very general free motion speaks strongly against 

 the adoption of this opinion. 



II. A much smaller corneous piece, the TROCHANTER (PI. XVI. 

 f. 1, 6), stands in moveable connection with the coxa. The form of 

 this part is subject to many changes ; we sometimes rind it quite 

 annular, with surrounding, equally high sides ; sometimes compressed 

 and obliquely truncated, or prolonged into a lateral point (Carabus, 

 Dyticus}. This form is found chiefly among the beetles; in other 

 orders (the Diptera, for example) it has very generally the annular 

 form. In these orders, the articulation of the coxae consists only of a 

 firm membrane ; but in the former, ball-joints appear to be fitted to 

 corresponding sockets, whereby the strength of the union is very much 

 increased. 



III. The trochanter is succeeded by the THIGH (femur, PI. XVI. 

 f. 1, c), which is the largest joint of the leg. It is generally of a cylin- 

 drical, but not always equally thick, frequently knobby or clavate, 

 form. It is very often much longer than the two first joints toge- 

 ther; in general also longer than the following, but always thicker and 

 more robust. Besides this roundish form, we also observe angular, pris- 

 matic, parallelopipedal, flat, very much compressed, and provided with 

 a longitudinal furrow, or even globose and elliptical forms. Its union 

 with the trochanter is sometimes very close, at others looser. We meet 

 with its firm conjunction in the Coleoptera. In these the motion of 

 the thigh appears to be very limited, and in general the trochanter 

 moves in the articulation upon the coxae, when the thigh is touched ; 

 it is different in the Diptera, in which the freer union of both admits of 

 greater motion. The upper surface of the thigh is like that of the coxa 

 and trochanter, generally smooth ; but its margins are not rarely armed, 

 sometimes with solitary spines, sometimes with hair, or with long cilia. 

 Some have broad lobate appendages ( Trachusa lobata, Mantis oratorio). 

 We do not usually observe such processes upon the two first joints, for 

 coxa? armed with a spine belong to the rarer exceptions ; these we 



