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TEXT-BOOK OF ENTOMOLOGY 



special muscles of flight are attached, and thus the wings, after the 

 last nymphal moult, have the power of flapping, and of sustaining 

 the insect in the air ; they thus become true organs of flight. 



It is to be observed, then, that the wings in all herninietabolous 

 insects are outgrowths from the notum, and not from the flanks 

 or pleurum of the thorax. There is, then, no structure in any other 

 part of the body with which they are homologous. 



The same may be said of the true 

 Neuroptera, Trichoptera (Fig. 157), the 

 Coleoptera, and the Diptera, Lepidop- 

 tera, and Hymenoptera. As we have 

 observed in the house fly, 1 the wings 

 are evidently outgrowths of the meso- 

 and metanotum ; we have also observed 

 this to be most probably the case in 

 the Lepidoptera, from observations on 

 a Tortrix in different stages of meta- 

 morphosis. It is also the case with 

 the Hymenoptera, as we have observed 

 in bees and wasps ; 2 and in these 

 forms, and probably all Hymenoptera, 

 the wings are outgrowths of the scutal 



FIG. 157. Development of wings of region of the notum. 

 Trichoptera : A, portion of body -wall of 



young larva of Trichostegia ; cA/cuticula, With these facts before US W6 may 



forming at > a projection into the hypo- . " 



derails, m ; r, and d, forming thus the speculate as to the probable Origin of 

 first rudiment of the wing. , the parts in 



a larva of nearly full size ; a, c, d, b, the the WlllgS of insects. The V16WS held 

 well-developed hypodermis of the wing- 

 germ separated into two parts by r, the by some are those of Gegenbaur, also 



penetrating extension of the cuticula ; v, , , nl T ii i n 



mesoderm. C, wing-pad of another Phry- adopted by LubbOCk, aild Originally by 



ganeid freed from its case at its change to 

 the pupa ; l>, d, outer layer of the hypo- 

 dermis (m) of the body-wall ; , inner 

 layer within nuclei. After Dewitz, from 

 Sharp. 



myself. 3 According to Gegenbaur : 



"The wings must be regarded as homolo- 

 gous with the lamellar tracheal gills, for 



they do not only agree with them in origin, but also in their connection with 

 the body, and in structure. In being limited to the second and third thoracic 

 segments they point to a reduction in the number of the tracheal gills. It is 

 quite clear that we must suppose that the wings did not arise as such, but were 

 developed from organs which had another function, such as the tracheal gills . 

 I mean to say that such a supposition is necessary, for we cannot imagine that 

 the wings functioned as such in the lower stages of their development, and 

 that they could have been developed by having such a function." 



1 On the transformations of the common house fly, by A. S. Packard, Jr. Pro- 

 ceedings Boston Society of Natural History, vol. xvi, 1874. See PI. 3, Figs. 12, 126. 



2 See our Guide to the Study of Insects, p. 66, Figs. 65, 66. 

 Our Common Insects, 1873, p. 171. 



