174 



ANIMAL LOCOMOTIOlSr. 



The wings of insects can be made to oscillate within given 

 areas anteriorly, posteriorly, or centrally with regard to the 

 plane of the body; or in intermediate positions with regard to 

 it and a perpendicular line. The wing or wings of the one 



^5 



Fig. 92. 



e X 



Fig. 93. 



Fig. 92.— Right wing of Beetle {GoUatJius rnicans). dorsal surface. This wing 

 somewhat resembles the kestrel's (fig. 61, p. 186) in shape. It has an ante- 

 rior thick margin, d e /, and a posterior thin one, b a c. Strong nervures 

 run along the anterior margin (r^), until they reach the joint (e). where the 

 wing folds upon itself during repose. Here the nervures split up and di- 

 varicate and gradually become smaller and smaller until they reach the ex- 

 tremity of the wing (/) and the posterior or thin margin (5); other ner- 

 vures radiate in graceful curves from the root of the wing. These also 

 become finer as they reach the posterior or thin margin (c ci). r, Root of 

 the wing with its complex compound joint. The wing of the beetle bears 

 a certain analogy to that of the bat, the nervures running along the anterior 

 margin {d) of the wing, resembling the humerus and forearm of the bat (fig. 

 94, c?, p. 1T5), the joint of the beetle's wing (e) corresponding to the carpal or 

 wrist-joint of the bafs wing (fisr. 94, e), the terminal or distal nervures of the 

 beetle (/ b) to the phalanges of the bat (fig. 94, / b). The parts marked fb 

 may in both instances be Hkened to the primary feathers of the bird, that 

 marked a to the secondary feathers, and c to the tertiary feathers. In the 

 wings of the beetle and bat no air can possibly escape through them during the 

 return or up stroke. — Original. 



Fig. 93, — Right vnng of the Beetle {Goliathus micanfi). as seen from behind 

 and from beneath. When so viewed, the anterior or thick margin {d f) and 

 the posterior or thin margin (b x c) are arranged in different planes, and form 

 a true helix or screw. Compare with figs. 95 and 91 .—Original. 



side can likewise be made to move independently of those of 

 the opposite side, so that the centre of gravity, which, in 

 insects, bats, and birds, is suspended, is not disturbed in the 

 endless evolutions involved in ascending, descending, and 

 wheeling. The centre of gravity varies in insects according 

 to the shape of the body, the length and shape of the 

 limbs and antennae, and the position, shape, and size of the 



