Of) 



and left of the opening of the mouth in the form of three-cornered blades, or 

 sharp prongs. These blades or prongs resemble so much the well-developed 

 mandibles of chewing insects that we can rightly regard them as such. Syrphn* 

 has, then, besides labrum, epipharynx, hypopharynx and labiimi, a pair of man- 

 dibles. Near the mandibles, united with the basal portion of the proboscis, are 

 two palpi. Since neither maxillae nor anything similar to them, are to be found 

 on the mouth-parts of Syrphus, we must consider the aforesaid palpi to be the 

 only remnants of the maxillae, since the latter always have palpi." * The above- 

 quoted remarks give no valid reason for regarding the parts under consideration 

 as mandibles, for the form which a part assumes in an animal has little value 

 in determining its homology in comparison with the worth, in such determ- 

 inations, of the position and attachments of the organ, the homology of which is 

 in doubt; and, in this case, the situation of the maxillary palpi so near the base 

 of the organs in question, together with the fact that the maxillae are present, 

 and attached at the base to their palpi in Eristalis (fig. 4), leads me to suppose 

 that the parts, which Meuzbier regarded as mandibles in Syrphus, were really 

 maxillae. This view is further supported by the figure ** which Menzbier gives, 

 and by Gerstfeldt's statement that the mandibles are more or less rudimentary 

 and united to the sheath of the proboscis, in the Syrphidae. 



The labium of Eristalis horticola (side view in fig. 1; section in fig. 1, fi' 

 and 7', /) is larger than the other mouth-parts, muscular, pubescent on the outer 

 or under side, and throughout its length run two tracheal stems and numerous 

 longitudinal muscles. Its under surface and the middle of its upper side are 

 strongly chitinized, but between these two portions the walls of the labium 

 are very flexible, as can be seen in the sections ft' and y 1 of fig. 1. At its 

 base the upper or inner surface of the .labium joins the under side of the 

 hypopharynx, at the point where the latter is jointed to the fulcrum; the under 

 or outer surface of the labium .passes (with a fold or two when the proboscis 



* "An den Seiten des Basalkegels der Unterlippe und mit ihm verwachsen liegen zwei 

 dicke Chitingebilde, die rechts und links von der Mundoffnung in Gestalt dreieckiger Sclinei- 

 den oder scharfen Hacken vorspringen. Diese Klingen oder Hacken gleichen so selir den 

 wohlentwickelten Mandibeln der kauenden Insekten, dass wir mit vollem Rechte sie als 

 solche deuten konnen. Syrplms besitzt also ausser Labrum, Epi- und Hypopharynx und 

 Labium noch ein Paar Mandibeln. Neben den Mandibeln, mit dem Basalkegel verwachsen, 

 sitzen zwei Palpen. Da weder Unterkiefer noch etwas ihnen almliches an den Mundtheilen 

 von Syrplius zu finden 1st, so miissen wir die erwahnten Palpen als einzige Reste der Unter- 

 kiefer betrachten, da Letztere immer Palpen besitzen." 

 ** See Menzbier' s pi. 3, fig. 3. 



