JOURNAL OF ENTOMOLOGY AND ZOOLOGY 9 
1762 Urocerus Geoffroy. 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 Sirex juvencus Linneus, by designa- 
tion of Curtis (1829). The type of Paururus Konow is the 
same (vide Rohwer, 191la) and the latter is therefore a syno- 
nym 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 posterior 
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 the 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 abdomen in front of the cornus 
deep and wider than long. 
obesus 0. sp. 
