532 W. L. TOWER, 



of undetermined genera. The Buprestidae (Bupresiis, Chrysohothris, 

 Ägilus), Carahidae {Carabus) , Elateridae {Elater, Melanotus) and 

 Curculionidae {Macropus, Mononychus) have the wings developing in 

 the same way as in Phymatodes, with slight variations in individual 

 species. All, however, conform strictly to this simple type of wing 

 development. An examination of other families of beetles will un- 

 doubtedly extend the list of genera and species wherein the wings 

 develop according to this type. It seems then that this "simple type" 

 of wing development is characteristic of several large and important 

 families of Coleoptera, and it may, I think, be taken as more character- 

 istic of the order as a whole than either of the two following types. 



2) Recessed type= Corethra type of Gonin (1894). 



A more complicated type of development is found in the Scara- 

 haeidae where I have observed it in Osmoderma scabra and Lachno- 

 sterna fusca, et al. The first stage of the development of the wing 

 in these beetles I have not been able to obtain and in every case 

 seen the wing disc was well developed. From the structure of these 

 discs in the Scarabaeidae and from what is known of the development 

 of similar structures in Diptera there is no doubt that the hypo- 

 dermis first thickens, invaginates to form a deep pocket and then 

 evaginates to form the fundament, which at the end of the process 

 comes to lie in a deep pocket or niche of the hypodermis opening 

 broadly against the cuticula (PI. 14, Fig. 11 al.a, eac. al; PI. 15, 

 Fig. 20). In the two species studied the wing disc is not a round 

 or oval shaped structure as in the Diptera, but is much elongated in 

 the anterior-posterior axis and occupies nearly the entire breadth of 

 the segment. In Figs. 11, 12 and 13 (PI. 14) are shown surface views 

 of the wings of 0. scabra made by reconstruction from serial sections. 

 In the later development of the wings of 0. scabra or L. fusca the 

 wing grows rapidly, at the beginning of the prepupal stage pushing 

 out and downward from its containing pocket between the hypodermis 

 and the cuticula. 



This type of wing development I have not found in any species of 

 Coleoptera outside of the Scarabaeidae, although several undetermined 

 species of Scarabaeid grubs show this form of wing fundament. This 

 type of development may be found in other families of Coleoptera, but 

 I doubt if it is of as wide occurrence as the preceding one. It does, 

 however, form a connecting link between the preceding and the fol- 

 lowing types of wing development. 



