21 



Returning to Lyda, there can be seen lying directly beneath the 

 parts and in the center, the distal end of the labrum-epipharynx 

 (Ir-cp). This is shown dissected out in Plate I, figure 2. The 

 so-called "braces" of the labrum are in the form of two distinct 

 bars. 



Plate II, with the exception of figure 6, represents the parts of 

 Lygaeoncmatus crichsonii dissected out. These parts are not 

 drawn to scale for the great difference in size does not make this 

 feasible. Figures i and 2 show, respectively, the left and right 

 mandibles. They are articulated to the head by a condyle, shown 

 in the figures. The mandibles are further connected to the head 

 by mandibular ligaments, not well shown in the drawings of this 

 saw-fly, but well seen in a species of the family Formicidae, 

 genus Aphaenogaster, here presented for that purpose 

 (Plate II, figure 6.) The mandibles, as in Lyda, are separate 

 from the other parts. They are folded together when at rest, 

 the difference in the structure of their inner margins making 

 this possible. 



The labium (Plate II, figure 3) is drawn from a dorsal or 

 inner aspect. Here is seen a hypopharynx (hyp). In the mem- 

 brane below occurs what has been called the sub-mentum {sm). 

 Beneath the hypopharynx and lymg beneath its curving edges, is 

 the mentum (/«). From it arise, as in Lyda, the glossa, the para- 

 glossa, and the four-lobed labial palpi. The maxilla, shown in 

 figure 4, has already been described. Attention should be called, 

 however, to the connecting membrane which unites it to the la- 

 bium. 



Plate II, figure 5, shows the labrum-epipharynx. It possesses 

 that peculiar chitinized portion extending in the membrane to the 

 other parts. This structure is common to all saw-flies studied. 

 It is called the "brace of the labrum," and has already been re- 

 ferred to. It varies from a structure consisting of two distinct 

 bars to one where the two have become fused into one solid 

 part. In Lyda (Plate I, figure 2) this "brace" is seen as two 

 bars connected near the labrum. In Lygaeonematiis erichsonii 

 (Plate II, figure 5) there is noticeable a tendency towards sep- 

 aration and also in Dolerus arvcnsis (Plate I, figure 6). In 

 Tenthrcdo riifopcctus (Plate I, figure 5) the "brace" occurs as 



