Descriptions of Tertiary insects / by T.D.A. Cockerell.

  • Theodore Dru Alison Cockerell
Date:
1908
Catalogue details

Licence: In copyright

Credit: Descriptions of Tertiary insects / by T.D.A. Cockerell. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    14/18 (page 312)
    deri / a little more basad in Nemestrina A., and distinctly more apicad in Ilirmoneura clatosa. (2) Subcosta similar in all the species of Ilirmoneura, but endiTig somwkat further from the apex in II. vulcanica (nearly 3” from tip of wing) and II. clausa', ending still further from apex in Nemestrina A. (3) Radius (Ti) is practically the same in all. In II. vulcan- ica it and the subcosta are very thick veins, contrasting with the other longitudinal veins, all of which are slender. (4) Radial sector, or Rj+3. Practically the same in all. In 11. vnlcanica it rises rapidly at the cross-vein, as shown in the figure. (5) Radial cell. In all vei-y long ; the cross-nervure, which in many Diptera is very short, having become greatly elon- gated, and also very oblique, so that it forms more than half of the upper side of the cell. In Nemestrina A. and Ilirmoneura B., as also in Prohirmoneura, the cell terminates at the point of origin of the second mediocubital cross-nervure; but in II. melanderi it falls a little short of this, and in II. vulcanica and clausa the distance is considerable. This is shown in the accompanying figures, where the little fork on the right side of the diagram is the end of the radial cell. (()) Third radio-medial cross-nervure. This nervure is absent or not preserved in Prohirmoneura. In II. melanderi it is very long, and looks like a branch of the radial .sector. In the othei'S it is oblique but much shorter, as is shown in the figures (the nervure connecting li, with M). (7) Media. In Prohirmoneura \t fork?,’, in Neones- trina A. it forks, but the branches are bulged outwards at the base; in Ilirmoneura B. the upper branch has been deflected basally by the cross-nervure, so that there is a small false cross- nervure at the bifurcation; in the other species the false cross- nervure is lartre, as the fiijures show. In II. clausa the branches of the media meet again, enclosing a cell. (8) Cuhitus. The l)ranching differs in its relation to the first cross-vein, as the figures clearly indicate, a verbal descrip- tion being unnecessary. It is remarkable that in this, as well as in some features of the media, the recent species, esj^cially Ilirmoneura B. and Nemestrina A., are nearer to the Prohir- moneura condition than are the Florissant fossils. The apical cell between the branches of the cubitus is open in all except II clausa. (9) Cubital cell is just closed in II clausa', in the others, narrowly open. According to my interpretation, the vein bounding it a])ically is a cross-nervure, and not a branch of the cubitus. If tins is correct, the vein which Comstock and Need- ham call C1I5 in Leptis, Dixa,Qtc,., is apparently this same cross- nervure, and their M, and Cu, are Cu, and Cii,.