530 



W. L. TOWER, 



5) Detached type with the fundament entirely cut ofiF from 

 the hypodermis and lying free in the body cavity. Melophagus (Pratt, 

 1900). 



Fig. E. Diagrammalic representation of the origin and development of the "detached 

 type" of imaginai disc. Modified from Pratt. 



In the Coleoptera the wings develop according to one of the first 

 three types, no species being known that shows the imaginai discs of 

 the last two types, which are known only in the Diptera. The devel- 

 opment of the wings in the larvae of Coleoptera I shall discuss by 

 types of development rather than by species and the probable signi- 

 ficance of these types I shall consider at the end of this section. 



1) Simple type. 



In Fhymatodes variabilis, Chrysohothris femorata, Buprestis rußpes, 

 and many other unidentified species of Ceramhycidae and Buprestidae, 

 during the formation of the first invagination a considerable area of 

 the hypodermis draws away from the cuticula but remains connected 

 with it by fine threads of chitinous material, which are secreted by 

 the cells as they more inward (PL 17, Figs. 27 and 28 cta^). The 

 proximal side of the fundament is supplied with small tracheal branches 

 from the dorsal longitudinal tracheal trunk; and leucocytes, blood 

 corpuscles, and cells resembling the "embryonic cells" of Verson (1890) 



