604 



THE STUD Y OF INSECTS. 



spect the homologous veins in the Lepidoptera and Diptera. In the 

 Hymenoptera the tips of the brandies of vein III coalesce with 

 other veins; and when this coalescence has proceeded for a con- 

 siderable distance towards the base of the wing, the branches may 

 appear like cross-veins, instead of branches of a longitudinal vein. 

 This result is very similar to what takes place in the more specialized 

 Diptera. In Pamphilus (Fig. 733) vein 1 1 I a is wanting; but this vein 

 is present in Macroxyela (mac rox-y-e'laj (Fig. 735). In both of 

 these genera there is a cross-vein between veins 1 1 1 1 and 1 1 1 2 +& (Fig. 

 733, cv). A similar cross-vein exists in some crane-flies, dividing cell 



IH4+V1 



Fig. 733. — Wings of a saw-fly. Pamphilius, with the veins numbered. 



IIIi into two parts (see Fig. 505). In both of these genera also the 

 tips of veins III 4 and 1 1 1 5 coalesce with vein Vi to such an ex- 

 tent that these veins appear to be cross-veins. In the wing of the 

 Honey-bee (Fig. 730) these veins are more obviously longitudinal 

 veins. 



Vein V is very similar to the homologous vein in the Diptera. It 

 arises from a cross-vein extending from vein III to vein VII. In 

 Pamphilius it arises from near the costal end of this cross-vein; but 

 in Apis (Fig. 730) its origin is near the middle of the cross-vein. In 

 the Hymenoptera, however, the cross-vein III— VII is much farther 

 from the base of the wing than it is in the Diptera. In the more 



