- 44 



is necessarily incorrect because his hypopharynx was the real epipharynx separated 

 by caustic potash from the labrum. Lowne 23 (p. 43) mentions and figures these, 

 processes which he terms " apodemes," aud, as he incorrectly supposed the 

 labrum-epipharynx, his operculum, to be made up of the labrum with a maxilla 

 coalesced on each side, he regards these " apodemes " to be the basal portions of 

 the maxillae. Thus from incorrect premises Lowne arrived at what I consider 

 to be a correct conclusion, that is, that these processes are the basal portions of 

 undeveloped maxillae. Macloskie' 24 regarded these same chitinous rods as the "great 

 tendons" of the mandibles, and then added (p. 159) the impossible idea, " This will 

 make the operculum represent two united mandibles, probably enclosing the labrum." 

 Macloskie correctly says, however, of these "great tendons," that they are to 

 the right and left of the fulcrum, and that they are slightly articulated to the 

 operculum. Menzbier 8 writes (p. 65) of these same parts, in a very indeterminate 

 manner, that, "they are simple muscle-tendons, which were less developed in 

 Syrplms, and consequently not described by us." * That these processes really 

 are the remnants of the basal chitinous supports of the maxillae is very probable, 

 because they are the only chitin-rods which occupy the relative position that is 

 occupied by the corresponding parts in other diptera (compare pi. 4, fig. 1, /?', 

 x with pi. 1, figs. 9 and 15,.ww,- and mp; pi. 2, fig. 1, i-k', x\ and pi. 3, fig. 1, 

 /-', x)\ because they are imbedded in a fold of the base of the labium; 

 because they are not firmly joined to the labrum, or to any other mouth-part ; 

 and lastly, because the maxillary palpi, altho not joined to these processes, are 

 above their distal ends, a position they would scarcely reach if these chitinous 

 tendons belonged to the mandibles or labrum. The maxillary palpi of Musca 

 are not joined to any firm supporting piece; the bridge or band of chitin, seen 

 at their base in pi. 4, fig. 1, is only a slight corrugation (as can be seen by 

 the section represented in pi. 4, fig. 1, /?', c-), which is probably due to the 

 hinderance to irregular folding, which would be otherwise caused at that point 

 when the proboscis retracts, by the presence of the palpi themselves. The 

 maxillary palpi of Musca, then, by some cause, are displaced from their basal 

 supports, which remain in their places, without maxillae or palpi, performing, by 

 the muscles attached to them, another function, that is, the lateral swinging of 

 the proboscis when the insect is feeding. 



The labium of diptera, their most fully developed mouth-part, and one that 

 is always present, joins the head below the other mouth-parts; its under wall 



* "Es sind einfach Muskelsehnen, die bei Syrphus weniger entwickelt und deshalb von 

 uns nicht beschrieben sind." 



