The 



origin and development of the wings of Coleoptera. 559 



Fig. 77), while the scales that were to remain white or yellow did not 

 have this gland associated with them (PI. 20, Fig. 73). 



6) Hind wings. The changes which occur in the hind wings 

 of the adult are not very extensive or significant. At the final 

 transformation all veins, scales, hairs, glands etc. are fully developed 

 and present no differences from those of the same structures of the elytra. 

 The veins, however, instead of becoming degenerate, show an aggre- 

 gation of the hypodermis, which soon begins to secrete the supporting 

 part of the vein, as described and figured by Comstock & Needham 

 (1899). 



The hypodermis does not degenerate to near the extent that it 

 does in the elytron, and the basement membranes remain in contact 

 (PI. 18, Fig. 52). Further, in the hind wings the hypodermis secretes 

 only a small amount of secondary cuticula so that the wings remain 

 light and flexible and have at the same time a maximum of strength. 



The hind wings of beetles often greatly exceed the elytra in 

 size and yet when not 

 in use are completely 

 hidden beneath the elytra. 

 In some forms the hind 

 wing is not larger than 

 the elytron and in these 

 it is not folded and has 

 a rather characteristic 

 venation (Fig. F). 



The mechanism by 

 which the wings become 

 folded is simple, but has not, I believe, been described. In Figs. G 

 and H are shown the expanded and folded hind wing of L. decem- 



Fig. F. Chrysohothris hind wing which is not 

 longer than the elytron and is never folded. Lettering 

 as in Fig. G. 



Fig. G. Hind wing of Leptinotarsa decemlineata extended ; cap. art articularjhcad^ 

 cot cotyla, sys.a anterior system of supporting veins, »ys.m median system of supporting 

 veins, sys.p posterior system of supporting veins. 



