JOURNAI^ OF ENTOMOLOGY AND ZOOLOGY 9 



1702 Uroccrus Geofr'roy. Hist, abreg. insec. de Paris; v. 2: p. 264. 

 1896 Paururus Konow subgenus. Verschied. aus der Hym.-Gruppe d. 

 Tenthred. < Wien. ent. Zeit; v. 15: p. 41. 



The type of the genus is Sir ex juvencus Linnaeus, by designa- 

 tion of Curtis (1829). Tlie type of Paururus Konow is tlie 

 same {vide Rohwer, litlla) and the latter is therefore a syno- 

 njTB of Sirex. 



The females of this genus are readily distinguished from 

 those of other genera by the shape of the cornus. Both sexes 

 are distinguished by the absence of white marks on the cheeks, 

 which I have found a thoroughly constant character. It is the 

 hardest of all genera in which to separate the males from each 

 other. Confusion has existed among them, and to some extent 

 continues. 



A Key to the North American Species of Sirex. 



FEMALES 



A. Abdomen blue. 



B. Legs black or blue, except sometimes apical half of po.sterior 

 tarsi. 



C. Cornus short and triangular or shouldered. 



D. From a side view the cornus is arched and dis- 

 tinctly widened before the apex, from above 

 short and triangular (Figs. 18 and 19). 



californicus (Ashmead) 



DD. From a side view tlie cornus is not arched, taper- 

 ing or at least scarcely widened before the apex, 

 from above short and shouldered (Figs. 20 

 and 21). 



E. In the front wings M„ separating from M, 

 midway between R^ and R- ; wings dark 

 violaceous, especially at the base and 

 along the costal margin; body short and 

 stout, the thorax very broad; second seg- 

 ment of the posterior tarsus shorter than 

 the two following united; impressed basin 

 on the alidomen in front of the cornus 

 deep and wider than long. 



obesus n. sp. 



