604 



THE STUDY OF INSECTS. 



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

 Hymenoptera the tips of the branches of vein III coalesce with 

 other veins ; and when this coalescence has proceeded fur 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 IILj is wanting; but this vein 

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

 these genera there is a cross-vein between veins IIIi and IIIo +5 (Fig. 

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



,11 



virr 



FIG. 733. Wings of a saw-fly, ranif>hilins, with the veins numbered. 



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

 tips of veins II I 4 and Ills 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 

 ve i n s. 



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 

 Painf>hilii:s 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 



