144 PROC. ENT. SOC. WASH., VOL. 23, NO. 6, JUNE, 1921 



In the studies made, by the author, on these appendages in 

 sawflies, he found them present in Tremex columba (Linnaeus) 

 but greatly reduced and inconspicuous (Plate XI, Fig. K). The 

 cerci are quite small, but are present as distinct, cone-like, 

 chitinous buttons on the membranous sternum of the tehth 

 urite. They are situated at the cephalad laterad angles of the 

 sternum of the segment in a position identical with that occupied 

 by them in insects where they are larger. 



The tenth tergite is arched, presenting a convex surface 

 dorsally, and its posterior margin is curved to produce a project- 

 ing semi-circular disk of chitin. Beneath the tergum there is 1 a 

 membrane lying close to it and connecting its posterior margin 

 with anus. Anus projects but slightly (never beyond the tenth 

 tergite) and is carried compressed, close to the membrane (tenth 

 sternite) below it, within the concavity made by the arching of 

 the tenth tergite (Plate XI, Figs. K and L). Thus, the entire 

 tenth sternum, including the cerci, is concealed beneath the 

 epiproct. 



EXPLANATION OF PLATES. 



A Urite X of larva of Pamphilimae, showing postcornu (cc) on epiproct 



(ep) and styli on hypoproct (hy). 



B Lateral view of postcornu of Siricidae, showing dorsal barbs. 

 C Lateral view of postcornu of Xiphydriidae, showing ventral barbs. 

 D Lateral view of postcornu of Cephidae, showing short, cylindrical, unorna- 



mented type with spines on basal lobe. 

 E Lateral view of postcornu of Pamphiliinae, showing anterior projection 



from the posterior median plate (mp). 

 F Leg of larva of Pamphiliinae. 



G Styli of larva of Pamphiliinae, appendages of the tenth urite. 

 H Urites IX and X of larva of Pteronidea ribesii showing epiproct (ep) with 



pseudocerci (pc) above anus (a) and postpedes (ppd) ventrad. 

 I Urites VIII-IX and X of pupa of Pteronidea ribesii showing epiproct (ep) 



above anus (a), hyproproct (hy) below anus bearing cerci (c), sheath 



(sh) and lancets (It). 

 J Urites IX and X of adult Pteronidea ribesii from venter showing cerci (c) 



below anus (a) and separated from tergum. 

 K Ventral view X urite of adult of male Tremex columba showing membranous 



sternite below anus (a) with cerci (c) at lateral extremities. 

 L Lateral view VIII, IX and X, urites of adult male Tremex columba. 



Key to Symbols. 



a anus. It lancets, 



c cerci. mp median plate, 



cc postcornu. pc pseudocerci. 



ep epiproct. ppd postpedes. 



hy hypoproct. sh sheath. 



