. Annual report. New York State Museum; Science; Science. REPORT OF THE STATE ENTOMOLOGIST I907 235 many aberrancies; and there is one here in the little group of genera of more typical Eriopterini shown on plate 23. The upcreep of the tips of the two veins under discussion toward the apex of the wing has already been rjoted in an earlier place for its effect upon the development of the cell ist M^. It is also noteworthy for having relieved the deflected base of M^+g of its ordinary responsibility. That deflected portion in Mesocyphona tends to atrophy, and thereby to reduce the rearward exten
. Annual report. New York State Museum; Science; Science. REPORT OF THE STATE ENTOMOLOGIST I907 235 many aberrancies; and there is one here in the little group of genera of more typical Eriopterini shown on plate 23. The upcreep of the tips of the two veins under discussion toward the apex of the wing has already been rjoted in an earlier place for its effect upon the development of the cell ist M^. It is also noteworthy for having relieved the deflected base of M^+g of its ordinary responsibility. That deflected portion in Mesocyphona tends to atrophy, and thereby to reduce the rearward extension of the cord. In like manner vein M^ is deflected upward just beyond its union with Cu^ and thereafter it tends to atrophy as in Dicranomyia, or to be reattached ? to vein M^+^ in the manner already discussed, and more fully illustrated in the accompanying diagram [fig. 16]. If any one would comprehend what has happened to the median vein in the Tipulidae, let him study the wings of the plates carefully in comparison with this diagram, a is the hy-. Fig. 16 pothetical typical media, with the dotted lines in this and in all the following indicating the positions of the cross veins. b, c, d and e represent the Ptychopterid line of specialization. h is Macrochile, with the media reduced to three branches; c is a hypothetical form introduced to account for the disappear- ance of the posterior division of the first median fork^. Material is lacking to fill this gap, and another interpreta- tion is possible: i. e. that, starting v^ith a form somewhat like Megistocera [pi. 16, fig. 4] the median cross vein has been lost and the branches have regularly and progressively fused to- gether, M^ and M^ completely, leaving these same two tips in Ptychoptera to be designated as M^+^ and M^. But the first interpretation is certainly admissible, from the frequent tend- ency of M^ and M* to atrophy; and it is rendered much the * This makes two tips of media remaining in Ptychoptera M^ and M^
Size: 2324px × 1075px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectscience, bookyear1902
