EXTERNAL ANATOMY OF INSECTS. 663 
b. Trochanter or Scapula*. ‘This is the second joint 
of the leo’: and if the coxa is regarded as the analogue 
of the thigh in vertebrate animals, this should seem to 
represent the patella or rotula, vulgarly called the knee- 
pan. Latreille and Dr. Virey consider this articulation 
as merely a joint of the cova”; but if closely examined, 
especially in Coleopterous insects, you will find it so 
fixed to the thigh as scarcely to have separate motion 
from it, and in many cases it seems to be merely its 
fulcrum; but I am not aware that any instance occurs in 
which it has not motion separate from that of the former 
joint. 
As to its articulation with the cora,—in the Coleo- 
ptera it appears to be of a mixed kind; for it imoscu- 
lates in that joint, is suspended by ligament to its ori- 
fice, and its protuberances are received by correspond- 
ing cavities in it; and its cavities receive protuberances, 
which belong to a ginglymous articulation. I have ob- 
served two variations in this Order, in one of which the 
motion of the thigh and trochanter is only in ¢wo direc- 
tions, and in the other it is nearly versatzle or rotatory. 
The Lamellicorns afford an example of the first, and 
the Rhyncophorous beetles or weevils of the second. If 
you extract from the cova the thigh with the trochanter 
of the larger species of Dynastes you will find that 
the head of the latter is divided into two obtuse incurv- 
ing lobes or condyles; that on the inner side being the 
smallest and shortest, and constricted just below its apex; 
and that under this is a shallow or glenoid cavity, ter- 
minating posteriorly in a lubricous flat curvilinear ridge. 
a Prare XIV. XV. XXVIII. q”. 
> N. Dict. d? Hist. Nat. xvi. 195. xxvi. 157. 
