62 



THE COCKROACH 



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.* 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 





Fig. 29. Wings and Wing-covers of Male Cockroach. X 4. 



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. 



* On wing-plaiting and wing-folding in Blattarue see Saussure, Etudes sur 1'aile 

 des Orthopteres. Ann. Sci. Nat., Ser. 5 (Zool.), Tom. X. 



