G44 EXTERNAL ANATOMY OF INSECTS. 



bute to fix the atmospheric fluid when the wings are 

 depressed in flight, while it glides over them as they 

 rise a ; in Ascalap/rus, Myrmeleo?i, Neraoplera, Hemero- 

 bim, Sec., the nervines are more visibly bristled ; the 

 bristles diverging on each side from the longitudinal ones, 

 but all pointing towards the apex from the connecting or 

 transverse ones; in Panorpa, besides these bristles, short 

 hairs, pointing the same way, are thickly planted in the 

 membrane of the wing ; and in Hemerobius the margins 

 of the wing are fringed ; in the Ephemerma, Corydalis, 

 &c, the wings are naked. In the Trichoptera Order, as 

 their name imports, they are covered with minute decum- 

 bent hairs, less easily seen but still existing in the se- 

 condary pair. In the Hymenoptera in general the wings 

 are covered with minute hairs or bristles ; but in Tiphia, 

 Scolia — with the exception of S. Radula and affinities in 

 which they are hairy — and others, the wings are nearly 

 naked ; in Pompilus, Pepszs, &c, the hairs are infinite- 

 ly numerous and very short ; in the Sphecidce, Mutilla, 

 &c, they are more distinct, longer, and less numerous; 

 in the humble-bee (Bombics) and many others the apex 

 of the wing is darkened by a large number of more con- 

 spicuous hairs, each of which seems to spring from a mi- 

 nute tubercle : as these tubercles are in a part of the wing 

 that is strengthened by few nervures, they may probably 

 be intended to supply their place, in giving firmness and 

 tension to this part. The 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 margin. In the first view, in Stra- 



a 4nalyse, 24. He seems to think that certain crooked hairs, in 

 soire wings, supply the place of folds. Ibia. 



