646 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



are very specialized in the region of the radial and radio-medial cross- 

 veins and in the arrangement of the cells of the hind wings in an 

 oblique row. 



Oryssidse. —A small family" consisting of four genera and a very 

 limited number of species found in all parts of the world. The family 

 is known to the writer only in the genera Orysxus (tig. 97), Ophryno- 

 2>>'''^i and the notes given here refer only to these genera. It has been 

 found that as a rule the figures of wings given by writers who have 

 not made an especial stud\' of wing venation can not be depended upon, 

 but, judging from such figures of species not accessible to the writer, 

 they would seem to indicate more generalized conditions than those 

 existing in Oryssi/s. The costal area is narrow; the costa is a delicate 

 vein quite strongly thickened at base; Sc+R+M is a strong vein which 

 functions for the costa, and at the origin of media it bends abruptly 

 toward the stigma; cubitus and Sc+R+M are coalesced for a short dis- 

 tance at the base of the wing ; the veins beyond and behind the stigma 

 are nothing more than dark bands of color; the transv^erse part of 

 media is almost entireh" wanting; the radio-medial cross-vein, the base 

 of the radial sector, the free part of R., and the transverse part of M^ 

 are entirely wanting. The weakening of these veins is undoubtedly 

 due to the thickening of the wing membrane. The second anal cell 

 has been reduced, probaVjly by the coalescence of the third anal with 

 the combined first and second anal. The base of R3 is joined to the 

 stigma b}^ means of the radial cross- vein, as was fully described in the 

 preceding pages. In the hind wings the costa is entirely wanting, 

 R+M is thickened and takes the place of costa; the cubitus and the 

 remainder of the veins are onl}' lines of color; the second anal is 

 entirely wanting; the third anal is preserved as a verj^ delicate line. 



So far as their wings are concerned the presence of the second anal 

 cell in the front wings is the only structure that would place the 

 genus Oryssas in the superfamil}' Tenthredinoidea. In their form 

 and topography thej^ are much more like the higher Hymenoptera 

 than the other Tenthredinoidea. It stands at the summit of special- 

 ization, so far as this group is concerned, as an extreme isolated line 

 of development. 



VII.— SUMMARY. 



In the course of the study presented in the preceding pages the fol- 

 lowing topics have been discussed: 



1. An historical consideration of those investigations that have had 

 to do with the development of a uniform nomenclature for the wing 

 veins of all orders. 



2. It has been shown how the complex hymenopterous wing has 

 been developed from a wing of the simplest type. 



3. How the apex of vein Rj has been gradually pulled awa}' from 

 the wing margin to form an appendiculate cell. 



