. The Wilder quarter-century book: a collection of original papers dedicated to Professor Burt Green Wilder at the close of his 25th year of service in Cornell University (1868-1893). Wilder, Burt G. (Burt Green), 1841-1925; Zoology; Anatomy; Physiology; Evolution; African Americans. Evolution and Taxonomy 65 broadly expanded so as to provide for a sliding flight, there is a necessitj' for the plaiting of these wings when not in use so that they may be carried without impeding locomotion on foot ; second, we find in certain cases where the tendency of spec- ialization has been towards a narrow
. The Wilder quarter-century book: a collection of original papers dedicated to Professor Burt Green Wilder at the close of his 25th year of service in Cornell University (1868-1893). Wilder, Burt G. (Burt Green), 1841-1925; Zoology; Anatomy; Physiology; Evolution; African Americans. Evolution and Taxonomy 65 broadly expanded so as to provide for a sliding flight, there is a necessitj' for the plaiting of these wings when not in use so that they may be carried without impeding locomotion on foot ; second, we find in certain cases where the tendency of spec- ialization has been towards a narrowing of the wings in order to admit of vigorous flight, a corrugation of the wings has taken place in order to strengthen them. The hind wings of a grasshopper illustrate the first ; and the wings of a dragon fly present the extreme of the second form of specialization. It is easy to see that a corrugated wing, like that of the dragon fl3', is much stiffer than it would be if the membrane extended in a single plane. If one will examine the cross veins ex- tending between the costa and the radius in a dragon fly, he will find that some of these are in the form of triangular braces which ef- fectually prevent any ten- dency on the part of the wing to become flattened. Evidently the corrugation is of extreme importance. The concave veins have arisen in two wa3'S. The first of these is by a change in the position of a convex vein. The subcosta in of the orders of insects is an illustration of this. In the Lepidoptera the subcosta has retained its form as a convex vein, but in most orders of insectst he area be- tween the costa and the radius has been depressed forming a furrow along the bottom of which the subcosta extends. This corrugation has resulted from the need of a stiffening of the costal edge of the wing. The second method of formation of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - color
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