EXTERNAL ANATOMY OF INSECTS. 669 
its end, which receives the head of the ¢zbia, is very con- 
spicuous in the weevils; but in no insects more than in 
Locusta*, in which tribe it deserves your particular at- 
tention. 
d. Tzbza or Cubitus*. The tibza or shank is the fourth 
joint of the leg, which according to the hypothesis lately 
alluded to is the analogue, in the anterior leg of the car- 
pus or carpal bones, and in the four posterior ones of the 
tarsus or tarsal bones of vertebrate animals. This may 
be called the most conspicuous of the articulations of the 
leg; for though it is generally more slender and often 
shorter than the thigh, it falls more under the eye of the 
observer, that joint being more or less concealed by the 
body: it consists in general of a single joint; but in 
the Araneide and Phalangide it has an accessory one, 
often incrassated at its base, which I have named the 
Epicnemis °. 
With respect to the articulation of the tzbta with the 
thigh—we may observe that in general it is by means of 
three processes or condyles, two lateral and one interme- 
diate, of the head of the former joint¢: the lateral ones 
are usually received by a cavity or sinus of the gonytheca 
of the thigh*; and upon these the ¢dca turns, with a 
semirotatory motion up and down as upon a pair of pi- 
@ Prate XIV. Fic. 5. and XXVII. Fie. 15. 7'”. 
b Pirates XIV. XV. XXVII. 3”. 
© Pirate XXVII. Fic. 21.5’. M. Savigny (Anim. sans Vertebr. 
1. 1.46. Note 4.) seems to think that this structure obtains in all 
his Apiropods; viz. the Octopod Aptera, Arachnida, and Myriapoda: 
but it seems to me evident only in the two tribes mentioned in the 
text. 
4 Prate XXVII. Fic. 6, 16, 17.7”. 
¢ Ibid. Fie. 15, 7”. 
