CHAPTER XXIV 

 THE WINGS OF THE DIPTERA 



(a) THE MORE GENERAL FEATURES OF THE WIXGS OF THE DIPTERA 



The most distinctive feature of the wings of the Diptera is the fact that 

 only the first pair are developed as organs of flight ; the second pair being 

 greatly reduced in size. The second pair of wings are known as the 

 halteres, they are thread-like, enlarged at the end, and are pnjbably organs 



Fig. 357. — Wing of Rhyphus. 



of special sense. They are present in nearh' all members of the order, even 

 when the front wings are wanting. 



The fore wings are thin, membranous, and usually either naked or 

 clothed with microscopic setae; but with mosquitoes the wings bear a 

 fringe of scale-like seta on the margin and usually also on each of the wing- 

 veins, and in the moth-hke flies (Psychodidae) and in some others the 

 clothing of setffi is very conspicuous. 



Fig. 358. — Wing of Rhynchocephalus. 



In the more generalized members of the order, the wing-venation is 

 simple, the only departures from the hypothetical primitive type being the 

 result of a reduction in the number of veins by the coalescence of adjacent 

 veins; this is well-shown by the wings of Rhyphus (Fig. 357). Neither 



(:M7) 



