337] LARVAE OF THE TENTH REDINOIDEA-rYV ASA 19 



{pit), where the postartis of the mandible articulates. The occipital suture 

 (os) when present originates in or near the postcoila. The postcoila is 

 always present. 



Paracoila. — There is a slight projection at the mesal end of the caudo- 

 ventral margin of the head where the cardo of the maxilla articulates. This 

 is the paracoila (pi). It is not well developed but is present and discernible 

 in nearly all tenthredinid larvae. . 



Odontoidea. — The lateral cervical sclerite is articulated with the head 

 capsule on the mesal margin of the postgena some distance ventrad of the 

 origin of the vertical furrow. This point of articulation is an odontoidea 

 (od) and is rather indistinct in the larvae of this group of insects. 



Tentorium— -The tentorium is very simple in tenthredinid larvae. 

 It consists of the metatentoria (m/), corpo tentorium (ci), and pretentoria. 

 The supratentoria are apparently obsolete. The metatentorium is the 

 strongly chitinized conspicuous ental bar extending into the head capsule 

 from the ventro-mesal margin of each postgena. The two metatentoria 

 fuse on the meson and form the bridge, the corpotentorium, which gives 

 support to the caudo- ventral portion of the head. The position of each 

 metatentorina is indicated by a pit- or slit-like depression (mn). The loca- 

 tion of the pretentorinae (pn) has already been indicated. A strong 

 ental arm, much smaller than a metatentorium, extends yentro-mesad 

 from each pretentoria into the head capsule and fuses with the corpoten- 

 torium near the middle of the latter. This bar is a pretentorium. In 

 ecdysis the tentorium breaks in the middle of the corpotentorium, freeing 

 the mesal ends of the pretentoria and metatentoria. The tentorium in 

 the Xyelidae and Pamphiliidae is similar to that of the Tenthredinidae in 

 structure and location. 



The movable parts of the head include all the appendages, that is, the 

 antennae, mandibles, maxillae, and labium. 



Antennae. — The antennae are present in the larvae of all Tenthredin- 

 oidea, but their structure, size, position, and number of segments vary in 

 the different families and subfamilies. Each is borne by a distinct anten- 

 naria (ar) which is located in the ventrolateral portion of the vertex; in the 

 generalized families they are located cephalad of the ocularia; in the 

 specialized, ventrad of them. The antennariae are usually subcircular or 

 subquadrate. The antacoria (an) is usually extensive, distinctly convex, 

 and whitish in color (Figs. 143-153). It is only occasionally narrow and 

 confined to the periphery of the antennaria, as in certain Nematinae 

 (Fig. 154). The antennae of the Pamphiliidae (Fig. 26) are setiform, 

 one-half as long as the head is wide, with seven cylindrical segments. 

 There is a circular sensorium on the ventral aspect, of the distal portion of 

 the second, third, and fifth segments (Fig. 39). In the Xyelidae (Fig. 27) ' 

 the segments are shorter but thicker, and vary in number from six to seven 



