EXTERNAL ANATOMY OF INSECTS. 6453 
in Pompilus, Pepsis, &c., the hairs are infinitely numerous 
and very short; in the Sphecina, Mutilla, &c., they are 
more distinct, longer, and less numerous ; in the humble- 
bee (Bombus) and many others the apex of the wing is 
darkened by a large number of more conspicuous hairs, 
each of which seems to spring from a minute tubercle: 
as these tubercles are in a part of the wing that is strength- 
ened by few nervures, they may probably be intended to 
supply their place, in giving firmness and tension to this 
part. ‘he wings of Diptera, under the present head, may 
be viewed with regard to the hairs that are implanted in 
the membrane of the wing, in its nervures, and in its mar- 
gin. In the first view, in Stratyomis and immediate 
affinities the wing is nearly naked; but in Xylophagus, 
Beris, and the great majority of the Order, the mem- 
brane of the wings is thickly planted with innumerable 
very minute bristles, not to be seen but under a power- 
ful 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 remarkably 
bristly’ at the base, with hairs intermixed ; in CGstrus 
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 Gastrophilus Equi the whole costa 
is covered with short decumbent hairs or bristles; in 
Musca pagana*, just at the apex of the costal areolet, that 
nervure is armed with a spur or diverging bristle larger 
* Meigen (Dipt. v. 16.) considers MZ. pagana as an Anthomyia ; 
but the insect referred to in the text is a true J4usca, and corre- 
sponds with the description of Fabricius in Ent. Sys. Em. particularly 
in its testaceous legs with black tarsi. 
AA Wig? 
