OF MAXILLULjE in the orders of insects. 



449 



This structure has been examined in various species, and considerable 

 diversity was found to exist. Perhaps the simplest condition was that met 

 with in Selandria sixii. The anterior portion of the labium (text-fig. 45) 

 bears the three-jointed palps, and is scarcely differentiated into a median (/.) 

 and two lateral portions (/>.</■)• The labium forms the ventral wall of a 

 wide depression (/.) at the base of which is the end of the spinning duct. 

 Dorsal ly this funnel is bounded by a rounded chitinous protuberance (h-), 

 which is connected laterally with a similar pair of lobes (?».) closing in the 

 sides of the funnel. They are the " glossa" and " paraglossia" respectively 

 of MeGillivray (31). Each lateral lobe measures - 48 mm. in length and 

 "46 mm. in breadth, f^rom their position in the floor of the mouth, and 

 above the labial duct, I conclude that the median structure is the hypopharynx, 



Text-fig. 15. 



Selandria sixii. Labium and hypopharynx, dorsal aspect, x 55. /(. Hypo- 

 pharynx. I. Ligula. m. ftlaxillula. l.p. Labial palp. p.y. Paraglossia. 



and that the laterally associated pair may be maxillulas or, at least, partly 

 maxillular in constitution. 



The mouth-parts of the larva of Nematus Erichsonii are typical of those 

 of the majority of Tenthredinese investigated. The surface of the hypo- 

 pharynx and its dorso-latcral lobes is membranous and of rounded 

 indefinite form. 



Tlie larva of Fenusa melanopoda was found mining the leaves of alder- 

 trees. When mature it measures 9 mm. in length. The internal structure 

 of the head bears a striking resemblance to that of the young Acrocecrops 

 Heinrich and De Gryse (loe. cit. pi. 3. figs. 4 & 2). The mouth-parts are 

 in both cases reduced and are associated with slender skeletal rods traversing 

 the entire length of the head. 



The mouth-floor of Fenusa melanopoda, viewed from above, presents the 



