MEINERT ON MOUTH-PARTS 45 



of the Diptera^ he adopts Bunneister's view that the labellae are homologous with 

 labial palpi. None of the recent authors have concurred in this view. The 

 three terminal lobes of the labium have been designated by Kellogg, who has 

 given a very clear exposition of the mouthparts of the Nemocera, as, medianly 

 the fused glossse, and, outwardly the paraglossse. This interpretation has been 

 followed by Wesche and others. Other details, such as the attempts to find 

 homologues of the components of the maxillae and labium of mandibulate in- 

 sects, can be passed over as purely hypothetical. 



All the authors who have endeavored to homologize the mouthparts of the 

 Diptera with those of the mandibulate insects have, with one exception, agreed 

 as to the fundamental parts, the labrum, hypopharynx, mandibles, maxillse, and 

 labium. 



John B. Smith, in a paper published in 1890, took an entirely different view 

 and defended this in a further paper which appeared in 1896. This interpreta- 

 tion has been adopted in a recent popular book on mosquitoes. He used the 

 mouthparts of certain highly specialized Hymenoptera and Coleoptera as a basis 

 for his homologies. Smith found in SimuUum, apically in the labrum, a pair of 

 small dentate chitinous structures which he considered rudimentary mandibles ; 

 these structures appear to be absent in all other nemocerous Diptera. He sup- 

 posed, not only that the parts usually considered mandibles are maxillary, call- 

 ing them laciniae, but that maxillary structures entered largely into the composi- 

 tion of the labial sheath. The parts supporting the labellae are said to be part of 

 the maxillae, the subgaleae, the labellae themselves the galeae. The labium is rep- 

 resented as a free piece, enclosed by the galeal structures, and the hypopharynx 

 united with it. Smith's work has been adversely criticized by the students of 

 dipterous mouthparts and moreover bears clear evidence that it was based merely 

 on rough dissections; only recently Leon, in a paper on SimuUum, discusses 

 Smith's homologies and points out the relationships of the parts in accordance 

 with modem studies. 



Meinert developed views at variance with all the other students and did not 

 believe that the mouthparts of the Diptera are homologous with those of man- 

 dibulate insects. While his interpretation is in the main controverted by the 

 histological work of Kellogg, it still seems of sufficient interest for a brief notice, 

 all the more as it has been generally ignored. 



Like all other modern investigators Meinert recognized that generally the 

 mouthparts of insects are homologous with the legs of the body and that, there- 

 fore, they are the exponents of distinct metameres. He demanded, however, 

 that to identify them with these, and those of the different orders of insects with 

 each other, something sufficiently characteristic should be in evidence and he 

 says: 



" I find this in the presence of a metamere and in the free jointing of the ex- 

 ponents to the under side of such a metamere, and according to this criterion 

 I test, whether the mouth-parts (that is the mouth-parts proper, the paired ones) 

 are homologous with appendages of the body on the one side, or among them- 

 selves on the other." 



