664 EXTERNAL ANATOMY OF INSECTS. 
If you next examine the trochanter in articulation with 
the coxa, you will perceive that the head of the former 
inosculates in it, that the lower condyle is received by a 
sinus of the coxa, which also has a lubricous very shallow 
cavity corresponding with the ridge, in which it turns; 
and in the head of the coxa, on the lower side, is an ex- 
ternal condyle, which is received by a sinus common to 
both, of the head of the thigh and of the exterior side of 
the trochanter *, in which it likewise turns: this last con- 
dyle has also an internal protuberance, which appears to 
ginglymate with a cavity of the trochanter: from this 
structure the leg is limited chiefly to a motion up and 
down upon two pivots, or to fold and extend itself. You 
will find an articulation very near this, but on a smaller 
scale, in the stag-beetle. In the other kind of articula- 
tion, which admits of freer motion, the head of the tro- 
chanter is prolonged, and the process terminates in a 
short interior condyle, which appears to work in a cor- 
responding cavity of the interior of the coxa; and the 
base of the process is encompassed by a ridge with a 
cavity behind it, which is received by another of the 
lower part of that piece, and admits a corresponding 
ridge—a structure that allows a rotatory motion. In the 
hind-legs of this tribe the motion is chiefly limited to 
folding and extending ; in Carabus, &c., also the head of 
the trochanter is nearly hemispherical, and the articula- 
tion approaches ball and socket. In most of the other 
Orders, the Hymenoptera excepted, there is little or no 
inosculation, the trochanter being simply suspended by 
ligament to the coxa as well as to the thigh ; its connec- 
tion with the latter is similar in Coleoptera; but in Ci- 
* Prats XXVIII. Fic. 12. b. 
