MOUTH-PARTS OF TOMOCERUS. 137 



guess-work, can identify as jaws and maxillae, and labium. 

 But in studying the parts rendered transparent, we can identify 

 the different appeudages. Figure 159 shows the common Tomo- 

 cerus plumbeus greatly enlarged (Fig. 160, seen from above), 

 and as the mouth-parts of the whole group of Poduras are 

 remarkably constant, a description of one genus will suffice for 

 all. The labrum, or upper lip, is separated by a deep suture 

 from the clypeus, and is trapezoidal in form. The mandibles 

 and maxillae are long and slender, and buried in the head, with 

 the tips capable of being extended out from the ring surround 

 ing the mouth for a very short distance. The mandibles (md, 

 Fig. 159) are like those of the Neuroptera, Orthoptera and 

 Coleoptera in their general form, the tip ending in from three 

 to six teeth (three on one mandible and six on the other), while 

 below, is a rough, denticulated molar surface, where the food 

 seized by the terminal teeth is triturated and prepared to be 

 swallowed. Just behind the mandibles are the maxillae, which 

 are trilobate at the end, as in the three orders of insects above 

 named. The outer lobe, or palpus, is a minute membranous 

 tubercle ending in a hair (Fig. 161, mp), while the middle lobe, 

 or galea, is nearly obsolete, though I think I have seen it in 

 Smynthurus, where it forms a lobe on the outside of the lacinia. 

 The lacinia, or inner lobe (Fig. 161, Ic; 162, the same enlarged), 

 in Tomocerus consists of two bundles of spinules, one broad 

 like a ruffle, and the other slender, pencil-like, ending in an inner 

 row of spines, like the spinules on the lacinia of the Japyx and 

 Campodea and, more remotely, the Iaclnia3 of the three sub 

 orders of insects above referred to. There is also a horny, 

 prominent, three-toothed portion (Fig. 161, gr). These homol- 

 ogies have never been made before, so far as the writer is 

 aware, but they seem natural, and suggested by a careful exam 

 ination and comparison with the above-mentioned mandibulate 

 insects. 



The spring consists of a pair of three-jointed appendages, 

 with the basal joints soldered together early in embryonic life, 

 while the other two joints are free, forming a fork. It is longest 

 in Smynthurus and Degeeria, and shortest in Achorutes (Fig. 

 172, 6), where it forms a simple, forked tubercle ; and is obsolete 

 in Lipura and Anura, its place being indicated by an oval scar. 

 The third joint varies in form, being hairy, serrate and knife- 

 like in form, as in Tomocerus (Fig. 159, a), or minute, with a 



