NO. 1438. WINGS OF THE'TENTHREDINOIDEA—MacGILLIYRAY. 643 



of Sirex. This vein is found besides in the Sirieid^e onl}^ in certain 

 species of the famil}' L3'did£e. It is noteworthy that it is situated 

 nearer the medio-cubital cross-vein than in the Lydidse, and that the 

 prominent l)ow in the base of cubitus, so characteristic of the Lydidjx?, 

 is wanting in the Siricidaj. The first and second anal cells approxi- 

 mate the type found in the tj^pical wing, but the emargination near 

 the base of the third anal vein, instead of being an abrupt one, as in 

 the typical wing, is a long, continuous curve. There has also been a 

 progressive migration of the free part of the second anal toward the 

 apex of the wing until in Paururus and Sirex californicus it is situated 

 midway between Mg+i and the medio-cubital cross-vein. In Xeris (tig. 

 89) it is just beyond the cross- vein, while in Tremex it is before. In 

 the hind wings there is in certain species a well-marked appendiculate 

 cell, but in Tremex and Paururus the transverse part of Rj has been 

 obliterated, leaving the cell Ri^., open at apex. This family is so spe- 

 cialized in most of its structures that it is of interest to Hnd at least 

 one of its characters very generalized. This is the point of origin of 

 media, which is more primitive than the same region in the Xyelidte 

 (figs. 31-35). There is a progres.sive migration from a position dis- 

 tinctly before the radial sector in Sirex eal if amicus, from the origin 

 of the radial sector in Paururus, and finally from the radial sector dis- 

 tinctly beyond its origin in Tremex. We find a confirmation of the 

 generalized condition of this character in its great variability, which 

 is not constant even in the same species. The first anal cell in Pau- 

 rurus and Sirex caJifomi c us \s oi the type described for the Lydida? 

 and Xiph3"driida% but in Tremex and Xeris the free part of the second 

 anal vein is entirely wanting. The explanation of the obliteration of 

 this vein is found in the following species: In Sirex alhievrnis the 

 basal two-thirds and the small transverse part is preserved; in *^//'^,t. 

 favicor?)is only the basal two-thirds is preserved, while in Xeris only 

 a part of the small transverse part remains. It should be noted that 

 in the three species just named the longitudinal part of this vein coin- 

 cides with the second anal furrow, along which this part of the wing 

 is folded, while in Paururus, where the entire free part of the second 

 anal vein is preserved, that the free part of this vein is distinctly before 

 the furrow. There is onl}^ one solution possible for the loss of this 

 vein, and that is that it is due to the presence and location of this fur- 

 row, which has migrated forward in certain species hand in hand with 

 the reduction of the anal area of the wing. That there is a marked 

 migration of this furrow and reduction of the anal area will be readily 

 seen by an examination of the wings of the difi'erent species of Treruex. 

 The genus Teredem " (fig. 90) possesses a number of interesting fea- 



«The figure of Teredon latitarsus was enlarged from a photomicrograph of the wings 

 of the type in the Collection of the American Entomological Society made and loaned 

 the writer by Mr. J. Chester Bradley. 



