672 EXTERNAL ANATOMY OF INSECTS. 



lateral condyle lately noticed : in the Dynastida this is 

 more prominent, and often forms a smaller segment of a 

 circle. In these also the protuberance of the thigh is 

 more minute, and its ridge is received by a cavity of the 

 tibia nearly semicircular a ; in Geotrupes Latr. the articu- 

 lation is not very different, though on a reduced scale ; in 

 Calandra Palm arum the lateral condyles of the tibia are 

 flatter and broader b ; and the articulatiou not being quite 

 so complex, this joint is kept steady by an intermediate 

 process observable in the gonytheca c . From the above 

 description it appears that the dislocation of the tibia is 

 effectually prevented in the Lamellicorns by the protube- 

 rance and ridge of the thigh working n their correspond- 

 ing cavities, while the condyle of that part turns with a 

 rotatory motion in the cavity of the thigh. In the Or- 

 thoptera Order the tibia is suspended by a ligament, in 

 the gonytheca the lateral condyles, which are very pro- 

 minent, working in a sinus of that part d . The subse- 

 quent Orders exhibit no very striking variations from 

 these types of articulation, I shall therefore not detain 

 you longer upon this head. 



With regard to the proportions and magnitude of the 

 joint we are considering,— the most general law is, that 

 the anterior pair should be shorter and more slender than 

 the intermediate; and the intermediate than the posterior; 

 and that all the tibia; should be shorter and more slender 



a Plate XXVII. Fig. 8. Thigh, a. Protuberance, b. Semicircular 

 cavity, c. Ridge. Fig. 9. Tibia, a. Central cavity, b. Ridge, c. Exte- 

 rior cavity. b lbid> FlG# g a c Ibid Fig> 7> a 



«' Ibid Fig. 15. Thigh ofLocmta Leach, a. Sinus in which the con- 

 dyle of the tibia works. Fig. 16. Tibia of Do. aa. Lateral condyles, 

 b. Intermediate one. 



