EXTERNAL ANATOMY OF INSECTS. G4-5 



tyomis and immediate affinities the wing is nearly naked; 

 but in Xylophagus, Beris, and the great majority of the Or- 

 der, the membrane of the wings is thickly planted with in- 

 numerable very minute bristles, not to be seen but under 

 a powerful lens, often black, and seemingly crowning a 

 little prominence, and giving the wing an appearance of 

 the finest net- work. As to the clothing of the nervures, 

 the costal, in Anthrax, Bombylius, &c, is often remark- 

 ably bristly at the base, with hairs intermixed; in CEst?'us 

 Ovis, in the inner margin or edge of this nervure, is a 

 single series of bristles, or rather short spines, like so 

 many black points; in (E. Equi the whole costa is co- 

 vered with short decumbent hairs or bristles; in Musca 

 pagana F., just at the apex of the costal areolet, that ner- 

 vure is armed with a spur or diverging bristle larger 

 than the rest, which is also to be found in many others 

 of the Muscidce, some of which have two and others more 

 of these spurs. The little moth -like midges (Psychoda 

 Latr., Hirtcca F.) at first appear to have the whole sur- 

 face of their wings covered with hairs ; but upon a closer 

 examination it will be seen that they are planted in the 

 nervures, from each of which they diverge, so as under 

 a lens to give it a very elegant appearance 8 . This fly 

 has its wings beautifully fringed with fine hairs, the 

 third circumstance to be attended to under this head; in 

 the Tipulidans, and many others of this Order, the apex 

 and posterior margin are also finely fringed with short 

 hairs. Some Dipterous insects make a near approach 

 to the Lepidoptera in the covering of their wings : in the 

 common gnat, when the wings are not rubbed, the ner- 

 vures are adorned by a double series of scales, and the 



■ Plate X. Fio. 13. 



