34 



epipharynx, a hypopharynx, a labium, and two maxillary palpi; mandibles and 

 maxillae are entirely absent. Menzbier says that the fulcrum is of "chitinized 

 processes of the wall of the pharynx." * Menzbier criticizes severely (p. 26-27) 

 several absurd statements made by Lowne, in regard to the proboscis of Musca, 

 but says nothing further of Lowne's work, leaving one under the impression, if 

 they depended for their information upon Menzbier's criticism, than Lowne's work 

 was only a mass of absurdities. 



Turning now from this brief historical summary of the progress of our 

 knowledge of the mouth-parts of Musca to the results of my ; own studies, based 

 almost wholly on the examination of the proboscis of M. vomitoria, I will describe 

 briefly the proboscis and its parts in the above-named species, omitting many 

 minutiae of structure, which it would be of little interest to mention in this 

 connection, because they would have neither value in determining homologies or 

 functions, nor use in the subsequent comparison of the mouth-parts of Musca 

 with those of the other diptera which I have examined. 



The proboscis of Musca vomitoria (side view of proboscis fig. i, of pi. 4) is 

 suspended from the under side of the head, and, like the corresponding organ of 

 Eristalis, can be extended and retracted by means of joints. The general external 

 aspect of the proboscis of Musca is like that of Eristalis ; the mode of its folding 

 by joints at the anterior under portion of the head and at the middle of the 

 proboscis, is, in almost every respect, the same as it is in Eristalis, and need not 

 be described here in detail. The most noticeable external difference between the 

 proboscis of Musca and that of Eristalis, a difference of limited morphological 

 value, - which one sees in a hasty examination of these two diptera, is that 

 the maxillary palpi of Musca are much larger, proportionally, than those of 

 Eristalis, are inserted much nearer the base of the proboscis, and are borne much 

 more erect from the proboscis, when the latter is extended, than they are in 

 Eristalis. Another noteworthy difference in outward appearance, but not one of 

 morphological worth, which is discovered between the proboscis of Musca and 

 Eristalis, is that, in the former of the two genera, the labrum-epipharynx is never, 

 by voluntary effort of the fly itself, extended above and free from the labium, so 

 that one sees, in a side view (fig. 1) of the apical half of the proboscis of 

 Musca, only the labium ; while in a side view (pi. 3, fig. 1) of the same portion of 

 the proboscis of Eristalis, one often sees the labrum-epipharynx, maxillae and labium. 



A cross-section through the proboscis of Musca, made at the point indicated 

 at a in fig. 1 and figured in fig. 1, a', exposes the labium (/) in the form of a 



* " Chitinisirte Fortsatze der Schlundwand." 



