. Diptera Nematocera (excluding Chironomidæ and Culicidæ). Diptera. EXTERNAL AKATOMT. 15 the great majority of genera in Tipulid-si, but occasionally closed (Mongoma) by the turning down of the 5th vein at its tip, meeting the 6th vein before tlie border of the wing. When open, therefore, it runs the whole length of the wing from the base to the wing-margin. Posterior to the 6th vein is the axillary cell. In TiPULiD^, in which the 7th vein is nearly always complete, that is to say, attains the margin of the wing, there is of course yet another cell—the last—in the hind angle of the wing. lu th
. Diptera Nematocera (excluding Chironomidæ and Culicidæ). Diptera. EXTERNAL AKATOMT. 15 the great majority of genera in Tipulid-si, but occasionally closed (Mongoma) by the turning down of the 5th vein at its tip, meeting the 6th vein before tlie border of the wing. When open, therefore, it runs the whole length of the wing from the base to the wing-margin. Posterior to the 6th vein is the axillary cell. In TiPULiD^, in which the 7th vein is nearly always complete, that is to say, attains the margin of the wing, there is of course yet another cell—the last—in the hind angle of the wing. lu those families of Diptera which have the 7th vein incomplete, all the space between the 6th vein and the hinder angle of the wing is considered the axillary cell (called by some of the older authors the " spurious '^ cell, presumably on account of its ill-defined nature). Some authors speak of a 1st and 2nd anal cell, plus an axillary cell. Where there has been occasion to mention this ultimate cell specially as such, it is herein called the 2nd axillary cell, thus retaining only one anal cell in the wing.* Wing pubescence.—A note may be made here regarding the terms " wings bare " or wings pubescent " in this family. It is probable that under very high microscopic power every wing will be seen to possess extremely minute stiff hairs, but when such are wholly invisible to the naked eye or to an ordinary entomo- logical hand-lens, the wing is considered bare, or, as some authors have termed it, glabrous ; and generally it is more or less iridescent. These microscopic setae are therefore never regarded as pubescence. When the naked eye or a hand-lens reveals distinct hairs on the veins or on the surface of the wing itself, the wing is considered pubescent. Practically all the veins bear microscopic short stiff hairs, but if these are not clearly seen without a microscope, the veins are not termed pubescent or Fig. 4.—The basal portion of a fl
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectdiptera, bookyear1912
