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



philiinae) and since it is a rather well recognized fact that the 

 uropods are true limbs, the author can see no reason for not 

 believing that the styli and postpedes are homologous struc- 

 tures (Plate XI, Figs. F and G). 



That the styli should differ considerably in general appearance 

 from the postpedes of an ordinary larva can not but be expected 

 when the differences of use are borne in mind (Plate XI, Figs. A 

 andH). In this respect it is to be remembered that the Cephidae 

 live in grass stems and twigs and that they line their galleries 

 with silk and that the Pamphiliinae make web nests, roll leaves 

 and make silk and leaf tubes, while those sawflies possessing 

 postpedes are usually free feeders, laying flat upon the surface of 

 the leaf, or holding to the edge with the apex of the abdomen 

 curled gripping the leaf or carried in the air curved S-shaped. 

 The styliform thoracic legs of the Pamphiliinae, in which the 

 claw is lost or changed in shape, resembles more closely the 

 arthostyli, than the well-developed thoracic legs of the free feed- 

 ing sawfly larva resemble the posterior uropods of these larvae. 



Cerci and Pseudocerci. 



Since the so called "cerci" of the larvae are not homologous 

 with the true cerci of the adult they should not bear the same 

 name, and since the "cerci" of larvae are without a name the 

 term "pseudocerci" 1 is suggested (Plate XI, Fig. H). 



The pseudocerci of the sawfly larvae, are much less regular in 

 presence, location and character than the cerci of the adult, a 

 fact which in itself would tend to throw suspicion upon their 

 being cerci. In the larvae of Pteronidea the pseudocerci are 

 wanting in some species while in others they are present and well 

 developed. In another Nematine genus (Pontania) the pseudo- 

 cerci of the larvae of some species approach each other quite 

 closely at the apex of the caudad margin of the epiproct and in 

 the Siricidae structures, which appear to be sufficiently similar 

 to bear at least tor the present the same name, are found situ- 

 ated to either side of the dorso-median caudal groove and 

 immediately above the basal lobe of the fold bearing the post- 

 cornu. The pseudocerci may easily be differentiated from the 

 cerci because they are always found dorsad of the anal opening, 

 and are always a continuation of the chitin of the epiproct 

 (Plate XI, Figs. H and J). 



Cerci of Tremex. 



Certain authors (Rohwer, MacGillivray and Bradley) have 

 remarked upon the absence of the cerci in the male of Tremex 

 and some have considered the absence of these appendages to 

 be of taxonomic importance. 



'Pseudocerci is a name for these structures suggested by G. C. Crampton in 

 a letter to S. A. Rohwer. 



