176 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



The three elements are developed to fairly equal proportions. 

 The arms of the mentum approach in general outline those of 

 Ectcedemia, but they are wider and the foot of the boot becomes 

 much larger. To each of these arms is connected a fleshy lobe 

 with the usual filaments and hairs along the anterior portion 

 and covered with bristly spines, arranged in parallel rows towards 

 the base. The lobes are attached to the upper edge of the hypo- 

 pharynx by means of transparent chitinous rods. The blades 

 projecting from and above these lobes are arranged in a longitudi- 

 nal row. The three front blades are short and broad, the others 

 are slender and finger-like, all arising from a common, narrow 

 base (cfr. pi. 17, fig. 3). 



The arms of the mentum in Acrocercops strigifinitella Clemens, 

 are very thin bands of chitin, presenting a ragged appearance at 

 their extremities. The lobes are developed to vast proportions 

 and a pronounced chitinization marks their line of junction to 

 the hypopharynx. The interior surface is finely striated, the ex- 

 terior being covered with filaments. The blades consist of a 

 row of translucent plates. They have moved to the apex of the 

 lobes. On examining these blades under oil-immersion it was 

 found that the two lower ones are placed so closely to the arms 

 of the mentum as to appear attached to these processes (cfr. 

 pl. 17, fig. 4). 



In an undetermined sesiid larva taken from the roots of cotton- 

 wood, we find the arms of the mentum quite long but projecting 

 only slightly over the hypopharynx. The lobes are reduced and 

 covered with spines. The blades are very similar in shape and 

 in texture to those in Acrocercops strigijiniteUa, but their line of 

 attachment corresponds better to that in the other gracilariid 

 larva described above (cfr. pl. 18, fig. 6). 



Layoa crispata, Papaipema nitela in the macro-lepidoptera 

 and Coleophora veroniaeella in the micro-lepidoptera are represen- 

 tative of the most commonly occurring type, with well defined 

 arms, fleshy lobes covered with spines but devoid of all traces of 

 blades (cfr. pl. 17, figs. 1 and 2 and text fig. 1). 



From their location in the buccal cavity we naturally assume 

 that the function of the organs described above is relative to the 

 feeding of the caterpillar. Most probably they facilitate the 

 entrance of food into the alimentary canal, maybe they are also, 

 in a certain measure, auxiliary to the mandibles in the mastica- 

 tion of the food particles. In none of the specimens have I found 

 muscles belonging to the maxillulse themselves (viz. lobes or 

 plates). 



It would appear then, that their movements are controlled 

 by the muscles attached to the mentum and its arms. In this 



