124 



ANIMAL LOCOMOTION. 



birds, all which goes to prove that sound is a concomitant of 

 rapidly vibrating wings. 



The Wing area Variable and in Excess. — The travelling- 

 surfaces of insects, bats, and birds greatly exceed those of 

 fishes and swimming animals ; the travelling-surfaces of swim- 

 ming animals being greatly in excess of those of animals which 

 walk and run. The wing area of insects, bats, and birds 

 varies very considerably, flight being possible within a com- 



FiG. 57.— Shows a butterfly with comparatively very large wings. The nervnres 



are seen to great advantage in this si^eeimen : and the enormous expanse of 

 the pinions readily explains the irregular flight of the insect on the principle 

 of recoil, a Anterior wing, h Posterior wing, e Anterior margin of wing. 

 /Ditto posterior margin, g Ditto outer margin. Compare with beetle, fig. 

 58. — Original. 



paratively wide range. Thus there are light-bodied and large- 

 winged insects and birds — as the butterfly (fig. 57) and heron 

 (fig. 60, p. 126) ; and others whose bodies are comparatively 

 heavy, while their wings are insignificantly small — as the 

 sphinx moth and Goliath beetle (fig. 58) among insects, and 

 the grebe, quail, and partridge (fig. 59, p. 126) among birds. 



The apparent inconsistencies in the dimensions of the body 

 and wings are readily explained by the greater muscular develop- 

 ment of the heavy -bodied short-winged insects and birds, and 

 the increased power and rapidity with which the wings in them 

 are made to oscillate. In large-winged animals the movements 



