66 Joh7i He7iry Co^nstock 



concave veins is illustrated by a vein that lies between radius 

 and media (vein IV), and also by a vein that lies between 

 media and cubitus (vein VI) in certain orders of insects. 

 These veins (IV and VI) I do not believe existed in the Palae- 

 odictyoptera ; at least, I have not been able to find any indi- 

 cation of their presence in the figures of paleozoic insects. 

 In the more modern orders of insects when a corrugation of 

 the wings arose, and the areas traversed by these veins be- 

 came depressed, veins IV and VI appeared. It is probable 

 that the}^ were developed by a straightening out of the zigzag 

 line between two series of cells. This can be readily seen by 

 comparing the wing of one of the devonian may flies (Plate III, 

 3) with that of a modern may-fly (Plate III, 5). In the devoni- 

 an may-fly the cells of the wing are polygonal, while in the 

 modern may-fly they are quadrangular. In the latter case 

 not only have longitudinal concave veins been formed from 

 zigzag lines, but the cross veins extending between these con- 

 cave veins and the adjacent convex veins have become strictly 

 transverse. An arrangement which insures the preservation 

 of the corrugations. 



In a similar way the concave veins in the anal area of the 

 modern Orthoptera have probably arisen. 



I conclude, therefore, that in the more highly specialized 

 wings of certain orders of insects, there exists a regular alter- 

 nation of convex and concave veins, this alternation being the 

 result of a corrugation ot the wings for the purpose of stiffen- 

 ing them. This conclusion is quite different than that 

 reached by Redtenbacher, who starts with the fan type of 

 wing as the primitive one. 



In the Lepidoptera this corrugation has not taken place, the 

 wings being stiffened by scales, consequently, the subcosta 

 remains a convex vein, and veins, IV and VI have not been 

 developed. It is probable that these veins are also lacking in 

 the wings of the Hymenoptera and the Coleoptera, but I have 

 not studied carefully the wings of these insects. 



As to the nomenclature of the wing veins of insects, there 

 is no longer any doubt regarding the desirability of a uniform 

 system of naming the veins in the different orders of winged 



