272 



THE WINGS OF A CICADA 



In the wings of a young nymph, on the other hand, the tracheae that 

 precede the veins are not massed as they are later; and in the older nymph, 

 where the forming veins appear as pale bands the cross-veins contain no 

 tracheae, and can be thus easily distinguished from the longitudinal veins. 



Figure 270 represents the 

 tracheation of the fore wing of 

 young nymph ; and Figure 271, 

 that of the hind wing. In each 

 of these figures the dotted line 

 a-b indicates approximately the 

 line along which the hinge of 

 the wing of the adult is formed. 



In the fore wing of this 

 young nymph the only depar- 

 tures from the typical branch- 

 ing of the tracheae are the 

 following ; trachea Ri coalesces 

 with the radical sector to a 

 point beyond the separation of 

 trachea R4+5; the first anal 



Fig. 271. — The hind wing of a young nymph 

 of a cicada (After C. & N.). 



trachea coalesces with trachea Cu for a short distance; and the second and 

 third anal tracheae are united at the base. These differences are remark- 

 ably slight compared with the great changes that have taken place in the 

 specialization of the mouth-parts and other organs of the adult cicada. 



In the hind wing the tracheation is much more reduced. An especially 

 striking feature is the complete loss of trachea Ri, which is considerably 

 reduced in the fore wing. 



In a wing of a mature nymph (Fig. 272) trachea Ri is completely aborted. 

 In fact one of the most characteristic features in the venation of the 

 Homoptera, and of the Heteroptera also, is the absence or very great reduc- 

 tion of vein Ri in the adult wings of most members of the order. The 



Fig. 272. — The fore wing of a mature nymph of a cicada (After C. & N. 



