MECHANISM OF THE WINGS 



153 



of movement ; the obliquity reaching its maximum in those portions of the 

 wings which move with the greatest velocity, namely, towards the extremities. 

 The result is that the wing becomes twisted at certain periods of the move- 

 ment." (See the fourth image in Fig. 168.) The position of the balancers 

 seems to vary according to that of the wings. (Marey's Movement, pp. 253-257.) 



Graber's views as to the mech- 

 anism of the wings, flight, etc. 

 Although in reality insects pos- 

 sess but four wings, nature, says 

 Graber, evidently endeavors to 

 make them dipteral. This end 

 is attained in a twofold manner. 

 In the butterflies, bees, and 

 cicadas, the four wings never act 

 independently of each other, as 

 two individual pairs, but they 

 are always joined to a single 

 flying plate by means of peculiar 

 hooks, rows of claws, grooved 

 clamps, and similar contrivances 

 proceeding from the modified 

 edges of the wings ; indeed, this 

 connection is usually carried so 

 far that the hind wings are 

 entirely taken in tow by the 

 front, and consequently possess 

 a relatively weak mechanism of 

 motion. The other mode of wing 

 reduction consists in the fact that 

 one pair is thrown entirely out 

 of employment. We observe this 

 for instance in bugs, beetles, 

 grasshoppers, etc. 



In the meantime, then, we may not 

 trust to appearances. As their devel- 

 opment indeed teaches us, the wings 

 as well as the additional members 

 must be regarded as actual evagina- 

 tions of the common sockets of the 

 body, and in order especially to refute 



the prevalent opinion that these wing-membranes are void of sensation, it should 

 be remembered that Leydig has proved the existence, as well as one can be con- 

 vinced by experiment, of a nerve-end apparatus in certain basal or radical veins 



