OF MAXILLUI^E IN THE ORDERS OF INSECTS. 



451 



unrecognisably modified to form the basal portion of the spinneret. Now 

 in larval Trichoptera the spinneret is intermediate in development between 

 that of Lepidoptera and the incipient condition of Tenthredinere. It there- 

 fore appears likely that in the two orders in which a spinneret occurs it is 

 derived from such raw materials as are afforded by the state of the hypo- 

 pharynx and labium of Tenthredinese. Assuming this to be the case, the 

 hypopharynx of the latter order is homologous with the proximal portion 

 of that of Lepidoptera. We should then expect that the simple lobes borne 

 at the anterior lateral border of the hypopharynx in Tenthredinese would be 

 represented in a modified form in Lepidoptera, where they would occur 

 at the sides of the hypopharynx behind the base of the spinneret. In this 

 position we find the paired lobes considered by De Gryse as maxilluhe. 



It, therefore, appears to me probable that the lateral lobes we have described 

 in the mouth-floor of Tenthredinian larvae are homologous with the maxillulae 

 of Lepidoptera. 



Bibio pomonce. Hypopharynx, dorsal aspect. The outline of the labium is 

 indicated beneath the surface of the hypopharynx. h. Hypopharynx. 

 /. Apical processes of labium. in. MaxUlula. s. Sclerite supporting 

 maxillnla externally. 



DIPTERA. 



Bengtsson (2) announced the discovery of maxilla^ associated with the 

 endolabium in lipulid Phalacrocera, stating that the latter structure was 

 innervated by a pair of endolabial nerves arising from the sub- oesophageal 

 ganglion dorsal to the mandibular nerves. 



Traces of maxillulre were sought for in the larvse of various genera of 

 Nemoceran diptera. These included Chironomus, Tanypus, Bibio, Myceto- 

 phila, Tipula, Ptychopiera, and Simulium. In the majority of cases the 

 views of authors as to the exact limits of labium and hypopharynx were so 

 various as to render impossible any definite conclusion as to the presence of 

 maxilluhe associated with the latter. 



