H YMENOP TERA . 605 



generalized Hymenoptera vein V is three-branched, and veins V 2 and 

 V 3 are connected by a cross-vein, as in the Diptera ; but this cross- 

 vein appears like a longitudinal vein (Fig. 733). The tip of vein V 3 

 has migrated from its primitive position on the outer margin of the 

 wing to the anal furrow (vein VIII), and ends in this furrow at a 

 greater or less distance from the margin of the wing (Fig. 733); the 

 result of this migration is to pull the cross-vein V a -V 3 into a longi- 

 tudinal position. 



Vein VII coalesces with vein III for a considerable distance from 

 the base of the wing in Pamphilius (Fig. 733) ; but in Apis (ig. 730), 

 and in many other forms, it arises from the base of the wing. This 

 vein is two-branched, as in the Lepidoptera and Diptera. The tips 

 of the branches of vein VII have migrated from the margin of the 

 wing to the anal furrow (vein VIII), and for a considerable distance 

 along this furrow towards the base of the wing, so that both of these 

 veins (VIIi and VII 2 ) end in the anal furrow, far from the margin of 

 the wing; the result of this migration is to pull the cross-vein 

 Vs-VIIi into a longitudinal position. In Pamphilhts (Fig. 733) this 

 cross-vein is nearly longitudinal ; in Apis (Fig. 730) it is completely 

 so. In Pamphilius vein Vila is very short, but well enough de- 

 veloped so that there is no doubt regarding the homology ; but in 

 most Hymenoptera it has completely disappeared. 



In the area lying back of the anal furrow there also exists a 

 tendency for veins to coalesce at their tips ; this is well shown in both 

 fore and hind wings of Pamphilius ; and in the hind wings especially 

 the united tips of veins IX and XI have migrated towards the base 

 of the wing along the anal furrow (Fig. 733). 



The concave veins of the anal area (veins X and XII) are rarely 

 developed ; in the hind wing of Pamphilius there is a fold which 

 probably represents vein XII (Fig. 735). 



The Cells of the Wing. Having learned the venation of the wings 

 it is easy to number the cells. There are, however, a few special 

 terms that are used in works on this order ; the more important of 

 these are the following : 



In most Hymenoptera there is an opaque spot on the costa, a short 

 distance beyond the middle of the wing; this is the stigma (Figs. 734 

 and 735, s). The stigma lies between vein IIIi and the margin of the 

 wing ; it is probably the apical portion of cell II. In Figure 733 it has 

 not been blackened in order to show the course of vein IIIi'. 



Usually vein IIIi , after joining the costa at the end of the stigma, 

 does not again separate from it, but is joined by the tip of vein III 3 

 before the apex of the wing (Fig. 733). But in certain families the 



