EXTERNAL ANATOMY OF INSECTS. 827 



limited, in one case to the Hymenoptera and Diptera on- 

 ly ; and in various Orders there is nothing analogous to 

 the stigma or carpus, and all the other nervures of an in- 

 sect's wing have no analogue in that of a bird, but more 

 especially as M. Latreille seems to think with me on this 

 subject a , I have retained Linne's term for the marginal 

 nervure, and for most of the others have adopted those 

 of the great French Entomologist just mentioned. I 

 shall here only further observe, — and it seems to me an 

 observation of prime importance, in the determination of 

 the question of the analogy of the wings of insects, — that 

 they are not, as in birds, the fore-leg converted into an 

 organ of flight, but, like the wing of the Draco, an organ 

 superadded to the legs ; and, further, that the connection 

 is not with the fore-legs, but, as has been before ob- 

 served b , with the two posterior pairs. 



The Costa is usually the strongest of the nervures, 

 and that upon which the wing seems to be built ; but in 

 some cases, as in Blatta, Scutellera, Cynips, &c, it is re- 

 presented by the mere membrane of the anterior margin 5 

 in some Coleoptera, as in Geotrupes, Dytiscus, &c, its struc- 

 ture, except at the base, appears to be annular or nearly 

 so, at least a vast number of corrugations, running trans- 

 versely, are observable on its upper and lower surfaces ; 

 it is thus capable of greater tension and relaxation, and 

 more flexile. The stigma or carpus d , though most conspi- 

 cuous in the Hymenoptera Order, may be traced in some 

 Coleoptera, Heteropterous Hemiptera, the Libellulina, 

 &c. ; but it has no representative in the Orthoptera, Le- 

 pidoptera, Trichoptera, &c. The mediastinal is usually a 



a N. Diet, d' Hist. Nat. i. 251. b See above, p. 564, 578, 591. 



« Plate X. h: d Ibid. Fig. 4, 11, rri". 



2 s 2 



