CHAPTER YII 

 THE WINGS OF THE ORTHOPTERA 



(a) THE MORE GENERAL FEATURES OF THE WINGS OF THE ORTHOPTERA 



The two pairs of wings of the Orthoptera differ in structure. The front 

 wings are leathery or parchment-Hke, forming covers for the more delicate 

 hind wings. These wing-covers have received the special name tegmina. 

 The tegmina usually overlap, at least at the tips, when at rest. The hind 

 wings are thinner than the tegmina and usually have a broadly expanded 

 anal area, which is folded in plaits like a fan when at rest. Many Orthop- 

 tera have vestigial wings, and many are wingless. In the males of the 

 saltatorial Orthoptera, the Acridiidse, Locustidae, and Gryllidee, musical 

 organs have been formed by modifications of certain parts of the wings. 



Correlated with the modification of the fore wings into tegmina there 

 are striking modifications of the shape of these organs and of the venation 

 of the costo-subcostal area. The costal margin of the wing is usually more 

 strongly convex than it is in insects in which the front wings are more 

 efhcient organs of flight ; and the costal vein is either greatly reduced or not 

 at all developed. In fact, the part played by the costal vein in the forma- 

 tion of the fore wings of the Orthoptera is problematic. 



The subcostal vein, on the other hand, is usually well-developed, and 

 usually gives off many branches that extend to the costal margin of the 

 wing. In many cases, one of these branches is larger than the others and 

 arises near the base of the wing. This is regarded by some writers as the 

 costa. If this view is correct the costa in these cases is distant from the 

 margin of the wing ; and it, like the subcosta, often gives off branches which 

 extend to the margin of the wing. For data bearing on this point see the 

 figures illustrating the tracheation of the wings of n^nnphs given later. 



As some recent writers place the Blattidce and the saltatorial Orthoptera 

 in separate orders, I discuss the venation of the wings of these two groups 

 separately. I have not studied the development of the wings of any of the 

 Mantidae or of the Phasmidas, hence a discussion of the wings of tliese two 

 families is omitted. It is not probable, however, that these will present 

 serious difficulties. 



(6) THE WINGS OF THE BLATTID.-E 



The tracheation of the wings. — The tracheation of the wings of n\Tnphs 

 of cockroaches was studied by Comstock and Needham. As but little 

 additional data on this subject has been published, the present account is 

 based chiefly on the facts detennined by us jointly. 



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