1U8 TEETH ON LABELLA IX GLOSSINA. 



a long tube is formed, with a slit on the upper side (compare 

 Fig. 8, which is a diagi'ammatic transverse section of the labium 

 near the middle). The labium consists of two segments and the 

 labella, but without a comparison with Stomoxys, Musca, and 

 Asilus, it would be impossible to discern these elements in 

 Gloss'ma. The second segment and the labella (Fig. 2, c and /) 

 are together only about one-fifteenth of the length of the labium. 

 The sides of the labella, of the second segment, and of the most 

 distal part of the first segment are brownish and rather firmly 

 chitinised, so that the different sections are not easily distin- 

 guished one from another ; a narrow band at the upper margin 

 and an exceedingly short terminal portion of the labella are more 

 or less membranous ; the labella (Fig. 2, /) have a dark brown or 

 black area below just behind the cleft between them, and the 

 second segment has a pair of small, rather dark, oblique plates 

 on the under side (Fig. 2, e, and Fig. 9, h). Seen from the side 

 the labella are rounded at the end ; seen from below (Fig. 9, c) 

 the cleft between them is sometimes narrow and triangular, and 

 sometimes the labella lie close together. 



The inflated basal part of the first segment is somewhat 

 strongly chitinised on the sides and below, while the slender part 

 of the same segment is firmly chitinised below, with moderately 

 thin lateral walls. The bottom of the median groove is a rather 

 thick plate, which begins just below the base of the labrum, and 

 continues nearly to the end of the labium ; in the most distal 

 portion of the first segment, in the second segment, and on the 

 proximal part of the inner side of the labella this plate is very 

 strong, and covers not only the bottom, but the sides of the deep 

 groove, almost to its upper margin. Fig. 10 represents the right 

 labellum seen from the inner side ; a is the outer ventral wall 

 (the black spot) divided in the median line ; c the plate in the 

 bottom of the groove divided in the same way ; d is the- lateral 

 part of this plate, and e its incurved upper margin. The same 

 figure shows that the inner wall of the free part of the labellum 

 is sheathed with three plates (9), which are strongly chitinised, 

 and over the major portion of their surface adorned with a 

 considerable number of transverse rows of exceedingly small 

 teeth, thus presenting a certain resemblance to a rasp. All these 

 plates are prolongations of the plate in the groove, but the upper 

 and lower ones are narrowed basally and marked off at the 

 base by a suture allowing a slight degree of mobility. The 

 latei'al margins of all three plates are finely serrated (the number 



