96 PARTIAL ORISMOLOGY. 



the different kinds of elytra have the additional purpose of covering 

 the soft upper part of the abdomen. Therefore all insects provided 

 with wings only are entirely inclosed in a hard case, and., although 

 they possess wings, are equally unprovided with a protection against 

 exterior influences, as those genera and species which have no wings. 



The observations we are about to make upon the wings will refer to 

 their exterior perceptible construction, and their different forms and 

 clothing. The investigation into their progressive conformation, their 

 internal coherence, their functions, &c., belong to other divisions, and 

 will be treated upon in the proper place. 



In outward appearance, the wings present themselves as flexible, but 

 firm, dry membranes, which are traversed by various horny ribs. These 

 RIBS (costce}, or more properly VEINS (nervae), as they are, in fact, 

 vessels, but incorrectly called NERVES (nerod), arise all from the roots 

 of the wing, and through their main branches, of which we usually 

 observe two or three, they are connected with the thorax by articulation. 

 The first and most exterior of these veins is called the MARGINAL RIB 

 (costa marginalis, PI. XV. a, a), or, by pre-eminence, the RIB (cosla), 

 which forms its anterior margin when expanded, and extends from 

 the base to the apex. Jurine, who made use of particular names to indi- 

 cate the veins of the wings of the Hymenoptera, calls it radius ; and a 

 horny expansion of it in its course, which is particularly distinct in this 

 order, but which is also observable in others, he calls the POINT of the 

 wing (punctum, or carpus) ; but Latreille, and Kirby and Spence call it 

 STIGMA (PI. XV. f. 4, /3). The second vein originates close to the first, 

 and distinguishes itself from the rest, like the former, by its superior 

 robustness. Its course also is in a direct line towards the apex, but it 

 gradually diverges from the marginal vein ; so that the portion of the 

 wing enclosed by it, takes the form of a triangle. Kirby and Spence call 

 this the posfcosta (PL XV. f. b, b, b) ; Jurine, cubitus ; and Latreille, 

 itcrviif. internus. It also ultimately attains the apex of the wing. It is 

 seldom simple ; in the majority of cases it divides itself into branches, 

 so that the main stem ceases before it attains the disc of the wins; ; but 



O ' 



the branches extend from the separation, either continuing simply to 

 the end of the wing, or again ramifying. By means of these ramifica- 

 tions, a varied net-work is produced upon the disc of the wing, the 

 reticulations of which are tolerably constant in the several orders, 

 families and genera, and is therefore of importance for the determina- 

 tion and distinction of the groups. The spaces enclosed by these veins 



