The origin and development of the wings of Coleoptera. 523 



same tissue later forms the wings would indicate that after its rise 

 the disc becomes quiescent to the extent that it almost disappears as 

 a recognizable structure. 



From these observations, which are based solely upon L. decem- 

 Kneata, I believe that the wing discs are derived from some part of the 

 mesothoracic and metathoracic spiracles and that the rudiments of the 

 spiracles pass through a period of inactivity in the early larva before be- 

 coming the active, growing fundament of the wing. In a large part of 

 the species examined this resting stage seems carried to the extent 

 that the cells of the fundament revert to the condition, as regards 

 size, etc., of the surrounding hypodermis, so as not to be distinguish- 

 able from it. Then, after a period of rest, these cells begin to grow 

 and become the imaginai disc. This helps to explain the conditions 

 found in the larvae of several beetles, the account of which belongs to 

 another part of this paper. 



b) Growth and invagination in the Larva. 



The fundament of the wing has been observed in its early stages 

 by many authors in the larvae of Diptera, Lepidoptera and Hymeno- 

 ptera and they all describe the imaginai disc as arising as a thickened 

 portion of the hypodermis. Likewise, in the Coleoptera, the first trace 

 of the wing in the larva is a thickened disc-shaped area lying in the 

 pleural )-egion of the thoracic segments (Comstock & Needham 1899, 

 Krüger 1899, Needham 1900). In the Heterometabola I do not 

 know of any observations upon the origin or early stages of the wings. 

 Many authors. Graber (1867), Rehberg (1886), Packard (1898) and 

 others "have concluded that the wings of the Heterometabola are 

 dorsal backward outgrowths from the pleural or tergal portions of 

 the thoracic hypodermis" but as far as I know not one of these 

 authors has actually seen the first stage of the wing fundament, and 

 their conclusions have been almost entirely based upon a superficial 

 examination of larval stages, wherein the wings had already become 

 external structures and had quite possibly shifted from their primi- 

 tive position to one better adapted mechanically to the needs ol 

 the larva. 



In the Coleopterous larva the wing fundament will earliest be 

 recognized as a thickened plate of cells upon the pleurum of the 

 mesothorax and metathorax. At first the fundament may show a de- 

 cided concentric arrangement of the cells, such as has been described 



