Cockroaches of both sexes are provided with wings, which, however, are only functional in the male. The wing-covers (or anterior pair of wings) of the male are carried by the second thoracic segment. As in most _Orthoptera genuina_, they are denser than the hind wings, and protect them when at rest. They reach to the fifth segment of the abdomen, and one wing-cover overlaps the other. Branching veins or nervures form a characteristic pattern upon the surface (figs. 4, 29), and it is mainly by means of this pattern that many of the fossil species are identified and distinguished. The true or posterior wings are attached to the metathorax. They are membranous and flexible, but the fore-edge is stiffened, like that of the wing-covers, by additional chitinous deposit. When extended, each wing forms an irregular quadrant of a circle; when at rest, the radiating furrows of the hinder part close up fan-wise, and the inner half is folded beneath the outer.[71] The wing reaches back as far as the hinder end of the fourth abdominal segment. The wing-covers of the female are small, and though movable, seem never to be voluntarily extended; each covers about one-third of the width of the mesonotum, and extends backwards to the middle of the metanotum. A reticulated pattern on the outer fourth of the metanotum plainly represents the hind wing; it is clearly rather a degeneration or survival than an anticipation of an organ tending towards useful completeness. [71] On wing-plaiting and wing-folding in Blattariæ see Saussure, Etudes sur l’aile des Orthoptères. Ann. Sci. Nat., Sér. 5^e (Zool.), Tom. X. [Illustration: Fig. 29.--Wings and Wing-covers of Male Cockroach. × 4.] The rudimentary wing of the female Cockroach illustrates the homology of the wings of Insects with the free edges of thoracic terga, and this correspondence is enforced by the study of the development of the more complete wings and wing-covers of the male. The hinder edges of the terga become produced at the later moults preceding the completely winged stage, and may even assume something of the shape and pattern of true wings; it is not, however, true, though more than once stated, that winged nymphs are common. Adults with imperfectly developed wings have been mistaken for such. _Origin of Insect Wings._