THE 1'KOBOSCIS. 43 



At the anterior part of the basal joint a pair of bands partially 

 surround the proboscis (Plate II. Fig. 10, and Plate III. e.) 

 These bear six or eight stiff set, which act as vibrissae or 

 feelers. The great maxillary palpi are attached to the upper part 

 of the posterior edge of the bands, the anterior edge of which is 

 continuous with a thin scale, covered with curved hairs. The 

 scales and bands are undoubtedly homologous to a part of the 

 maxilla? of other insects. The remainder of the maxilla? seems to be 

 united with the labrum and to be supported by a pair of lever-like 

 apodemes or internal processes, which lie one on either side of the 

 pharynx, between it and the bands in question. (Plate II. Fig. 7.) 



I believe the basal joint of the proboscis, \vith the epistoma and 

 maxillse, form the third segment in both the larval and perfect forms of the 

 fly. In grasshoppers, the three segments, fcnned by the facial plate, 

 the epistoma and the labrum, are quite distinct in front and correspond 

 exactly to the parts I have so named. Moreover, the maxillse clearly 

 belong to a segment posterior to that which bears the mandibles, not only 

 in the fly but in other insects. This is quite plain in the cockroach. The 

 position of the labiuin, which consists most undoubtedly in great part of 

 a pair of modified limbs, indicates that it forms the most anterior segment 

 of all. 



The homology of the maxillae needs careful study and comparison with 

 other insects. In bees, especially Xylophaga, these organs consist of a basal 

 sheath, which partially surrounds the pharynx and bears a comb of stiff 

 teeth, as well as the palpi. Two lobes arise from this sheath, a small 

 superior one covered with hairs, and a large sharp-pointed spathulate lobe 

 with a straight superior edge, fitting against that of the opposite side, and 

 forming the upper lip. The band in the fly represents the ba*>al sheath, and 

 the comb of bees is replaced by the setas. The thin membranous scales are 

 homologous to the small superior lobes, and the long pointed scales united 

 in the fly to the labrum are clearly the homologues of the terminal lobes in 

 bees, although they have usually been described as the mandibles. My 

 friend .Mr. C. Stewart pointed out to me that the thin scales homologous 

 to the superior lobes are united with these organs in Rhingia, an arrange- 

 ment which seems common in the Syrphida3, and which puts the matter, I 

 think, beyond a doubt. 



The pharynx and maxilla? are both represented by corresponding 

 organs in the larva, (Plate II. Figs. 3 and 3, a and Z.) The 

 sucking organ , both in function and form, is too like the same 



