628 EXTERNAL ANATOMY OF INSECTS. 



very slender nervure, placed between the costa and post- 

 costa, sometimes terminating in the former 3 , and at others 

 in the latter b : in the Orthoptera, Lepidoptera, &c, how- 

 ever, and some others, it is a very conspicuous and prin- 

 cipal one b ; in the Hymenoptera it is obsolete, merging 

 in those nervures c . The Postcosta is the principal ner- 

 vure of the wing in Scutellera, but in Staphylinus it is 

 wanting; in Chalcis sispes it is the only true«nervure of 

 that organ, the others being represented by spurious 

 ones d . The externomedial and internomedial are some- 

 times distinct at their origin, but more frequently are 

 branches from a common stem. 



Having made these general remarks, I shall now con- 

 sider particularly the neuration of the wings in the dif- 

 ferent Orders, beginning with the Coleoptera. The first 

 thing that strikes the physiologist in surveying a wing be- 

 longing to an insect of this Order, is the general arrange- 

 ment of the nervures e ; which are so placed that the 

 required degree of tension may be given to every part of 

 this organ: thus some are nearly straight f ; others run in 

 a serpentine direction s • others are forked with one branch 

 recurrent and another proceeding onwards h ; others again 

 are insulated, or do not originate from the base of the wing, 

 or from other nervures, but are merely placed to strengthen 

 an open space of it': these nervures are also usually 

 broader and more substantial than those of the wings of 

 the subsequent Orders. Another striking circumstance 

 with regard to them is that the nervures form few or no 



» Plate X. Fig. 14. fr. " Ibid. Fig. 12. k\ 



c Ibid. Fig. 8. 9. d Jurine Hymenopt. t. v. Gen. 47. 



e Plate X. Fig. 4. i Ibid. a. n\ o\ Mbid.wr. 



h Ibid. /■. j Ibid. a. 



