The origin and development of the wings of Coleoptera. 563 



insects have not arisen from tracheal gills". He bases his assertion 

 largely upon the absence of tracheae in the wing fundament of insects, 

 remarking that "the wing(s) (fundament) are the only parts that lack 

 air tubes". The same view is adopted by Pancritius (1884). Müller 

 further asserts that the wings of insects have arisen as lateral pro- 

 longations of the dorsal plates of the segments. 



It is probable that the wings of insects are homologous with no 

 other tracheate structure, or at least no evidence has yet been put 

 forward which shows any such homology, and as for their origin ac- 

 cording to the Tracheal gill theory of Gegenbaur or the Müller- 

 Packard theory of lateral or dorsal prolongations neither has as 

 yet any evidence to support it. It is futile to hope for palaeonto- 

 logical evidence, and the only way in which we may possibly get 

 certain upon the question of the origin of insects wings is by a 

 careful comparative study of the conditions found in the late embryo 

 and young larva of the more generalized orders of insects, and until 

 we have this knowledge speculation as to the origin and homology of 

 the wings of insects is without foundation and unprofitable. 



From the data presented in this paper it follows that the wings 

 of Coleoptera present no very fundamental differences from those of 

 the Lepidoptera or other orders that have been studied, showing only 

 the specialization that is to be expected in any group of animals. 

 The chief stages and processes are in all respects perfectly comparable 

 to the same stages and processes in the Lepidoptera and other Holo- 

 nietabola, although obscured, shortened or prolonged to adapt them to 

 the needs of the particular species. These specializations and adap- 

 tations have, however, been described in their proper place, and 

 need not be rehearsed here. It is certain, however, that the elytra 

 are true wings and are homologous to the fore wings of other 

 insects. 



As a whole the wings of beetles are specialized by reduction, 

 nut only of veins, as shown by Comstock & Needham, but also of 

 nerves and sense organs and by complexity of ornamentation, the 

 scales, hairs and colors being of the simpler kinds. The wings are 

 then relatively simple in structure and the elytra only show speciali- 

 zation by addition, in adding a thick deposit of chitin. Although 

 relatively simple the ornamentation is extremely significant, and of 

 this I have written fully in another paper. 



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