THE WINGS OF COLEOPTERA 



299 



area of the former. This is doubtless due to the fact that the meeting of 

 the elytra, when at rest in a straight line along the middle of the back does 

 not admit of an expanded anal area. 



"The extent of the correspondence between the venation and the 

 tracheation of the hind wing of a full-grown pupa is shown by Figure 310. 

 The principal tracheae are within the veins, but the branches of these 

 tracheae extend irregularly through the wing. In the region where the 

 wing is to be folded the secondary vein-like thickenings are only partly 

 supplied with tracheae." (C. & N.) 



Contemporaneous with the publication of the series of articles by 

 Comstock and Needham, Kruger ('98) presented to the University of 

 Gottingen a thesis on the development of the wings of insects with especial 

 reference to the elytra of beetles. This author studied the development of 

 the wings of Tenehrio molitor and of two species of Lema; and, notwith- 

 standing the fact that he found that the hind wings and elytra arise simul- 

 taneously and develop in an exactly similar manner for a major part of the 



Fig. 310. — Hind wing of a pupa of a beetle (From C. & X.). 



lar\-al life, reached the unwarranted conclusion that the elytra are divergent 

 structures and not specialized wings. This conclusion was based on differ- 

 ences in structure between the fore wings and hind wings that appear late 

 in their development and which are correlated with the specialization of the 

 elytra as wing covers. 



Since the publication of the papers referred to above, several papers 

 have appeared in which the development of the wings of Coleoptera are 

 discussed; these are by Needham ('00), Tower ('03), and Powell ('04)- 

 As these all confirm our conclusion that the elytra are modified wings, and 

 as none of them discuss the homologies of the wing veins, it is not necessar}^ 

 to review them here. 



The elytral tracheation of the tiger beetles (Cicindelidae) has been 

 described in two papers by Shelf ord ('13 and '15). These studies are based 

 on examinations of adult dried elytra. In only two genera {Amblychila and 

 Mantichora) were all of the six principal tracheae found. Of course the 

 basal connections of the tracheae could not be seen. 



