THE GENERAL FEATURES OF WINGS 



69 



complex, may be desirable in detailed taxonomic work; but for the pur- 

 poses of ordinary descriptions a designation indicating the most obvious 

 element of the compound vein is sufficient. Thus in the hind wing of 



/st A 

 Fig. 54. — Hind wing of an ichneumon-fly. 



Exetastes (Fig. 54), where veins M3, M4, Cui, Cuo and 2d A coalesce with 

 the first anal vein the united tips of these veins is designated, by the 

 term indicating its most obvious element, ist A. 



Serial veins. — In the wings of some insects, where the wing-venation 

 has been greatly modified, as in certain Hymenoptera, there exists what 

 appear to be simple veins that in reality are compound veins composed of 

 sections of two or more veins joined end to end with no indication of the 

 point of union. For compound veins formed in this manner I propose the 

 term serial veins. The following comparatively simple example will sen^e 

 as an illustration of a serial vein. 



In those Hymenoptera in which the wing-venation is not greatly reduced 

 vein M2 of the fore wings extends in a transverse direction from the point 

 of separation from vein Mi 

 to the point where it is 

 joined by the medial cross- 

 vein ; it then bends more or 

 less abruptly and extends in 

 a longitudinal direction. 

 This condition persists in the 

 fore wing of an ichncmon- 

 fiy (Fig. 55). But in the fore 

 wing of a braconid (Fig. 56) 

 the transverse section of vein 



M, has been lost; and the p^^ --._wings of an ichneumon-fly. 



longitudinal section of this 



vein and the medial cross-vein form together what appears to be a simple vein. 



The example just cited is perhaps the most easily understood of all of 



the serial veins. But there are cases where sections of several veins enter 



