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Fig. 150.—Diagrammatic reproduction of Fig. 149 showing the wing-germ in its peripodal cavity (p): h’drm, hypodermis; tr, trachea; cta, cuticula; a, anterior end.—After Mayer.
Fig. 151.—Section of the wing-germ, the upper and lower sides connected by spindle-like hypodermic cells (h), forming the rods of the adult wing; mbr, ground-membrane of Semper.—After Mayer.
f. The primitive origin of the wings
Farther observations are needed to connect the mode of formation of the wings in the holometabolous insects with the more primitive mode of origin seen in the hemimetabolous orders, but the former mode is evidently inherited from the latter. Pancritius remarks that the development of the rudiments of the wing in a hypodermal cavity is in the holometabolic insects to be regarded as a later inherited character, the external conditions causing it being unknown.
Fritz Müller was the first to investigate the mode of development of the wings of the hemimetabolic insects, examining the young nymphs of Termites. He regards the wings as evaginations of the hypodermis, which externally appear as thoracic scale-like projections, into which enter rather late in nymphal life tracheæ which correspond to the veins which afterward arise.