. 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 Taxorwniv. 11 Not only may the branches of one system of veins become joined to those of other systems as just described, but there are many forms in which two adjacent principal veins are coalesced to a greater or less extent. This occurs chiefly in the hind wings, I will discuss the veins in regula
. 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 Taxorwniv. 11 Not only may the branches of one system of veins become joined to those of other systems as just described, but there are many forms in which two adjacent principal veins are coalesced to a greater or less extent. This occurs chiefly in the hind wings, I will discuss the veins in regular order, beginning with costa. This vein is apparently' wanting in the hind wings of most L,epidoptera, and but little can be said regarding the manner of its disap- pearance. It seems probable that in most cases it has simply become atrophied, the overlapping of the wings rendering it unnecessary or even undesirable. For when that stage in the development of the order was reached in which the two hind wings of each side overlapped to a con â siderable extent, was it not better that the costal margin of the hind wing should be flexible ? There was no longer any need of a stiff margin, this part of the wing being sup- ported during the downward stroke by the overlapping part of the fore vi'ing ; while a flexible margin would act as a valve to prevent the escape of the air between the two wings. The two wings in this wa^- present a continuous surface. In many moths there is a thickening of the basal part of the costal margin ; this I believe to be the remnant of costa. But although it seems probable that in many cases the costa of the hind wings has simply faded out leaving cell I to function as this costal valve, there are cases in which this valve is a precostal development, the costa having moved. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustratio
Size: 1487px × 1681px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
