NO. H3.S. ir/AVnS OF THE TENTllREDlXOlDEA—MAciULLIVHAY. 623 



the base of the wing- and the stigma, where it turns abruptly toward 

 the margin of the wing. The free part of the vein Sc^ and the cell Sc 

 have been suppressed l\y the close approximation of the stems of Sc 

 and R+M. 



Lyd'ida^. — The Lydidie is an easily circumscribed family of ten 

 genera and a))out one hundred and twenty -five species which are 

 peculiar to the northern hemisphere. This and the Xyelida? are the 

 only families of Hymenoptera in which subcosta has been preserved 

 in the hind wings (tigs. 36-43). In this character the Lydida? are more 

 generalized than the Xyelida?. The series of wings here shown are of 

 value as indicating the manner in which the subcosta of the hind wings 

 has been suppressed, namely, by atrophy from the base toward the 

 apex. This family is noteworthy for the retention in man}- species of 

 the free part of Cu.^, though this character has been preserved in a lim- 

 ited number of species of the family Siricida; (tig. S()). The Lydidae 

 have departed farther from the tyical hymenopterous wing, and 

 are therefore more specialized than the X3'elida\ This is shown by 

 the origin of media much nearer the origin of the radial sector, so 

 that the cell R is only about as long as wide; l)y the position of the 

 posterior end of the radial cross-vein, which varies from a position 

 on the apical two-thirds of the cell R- to a position interstitial with 

 the free part of the vein R^; by the position of the anterior end 

 of the medio-cubital cross- vein at or just beyond the origin of the 

 media; by the loss of the free part of Rg", by the coalescence of the 

 tip of R^ for a greater distance from the margin of the wing; by the 

 difference in the shape and position of the cell M^ due to change in 

 position of the stem of media and of the medio-cubital cross- vein; in 

 the hind wnngs by the greater coalescence of the stem of media and 

 the radial sector; and by the greater constriction of the apex of the 

 tirst anal cell of the hind wings due to a coalescence of the first and 

 second anal veins. The loss of the free part of the second branch of 

 cubitus is a gradual one. It is complete except for the point where 

 it is crossed by the anal furrow in Liolyda (fig. 43), PampJulius (tig. 

 39), and Bactmceros (fig. 41); in Lyda (fig. 37) and Cephaleia (fig. 42) 

 the posterior half is wanting; in C^nolyda (fig. 38) it is only a small 

 tubercle on the posterior side of cubitus, while in yeurotoina (fig. 36) 

 and Itycorsia (fig. 40) there is left only the convexity, indicating 

 where the free part of Cu2 was situated. The Lydida? differ from the 

 specialized Tenthredinoidea in the preservation of subcosta of both 

 wings, the origin of media, the shape of the cell 1st Rj-j-Rg and the 

 course of the radial ci'oss-vein. 

 Proc. N. M. vol. xxix— 05 41 



