TEETPI ON LABEL LA. Ill 



(Fig. 21, 7nP ; Fig. 17, c), and by the contraction of this pair of 

 muscles the distal end of the labrum is raised. From the base 

 of the upper wall of the labrum a muscle (Fig. 17, e ; Fig. 21, m^) 

 runs upwards to the ' frontal part t)f the lateral wings of the 

 jjharynx ; the contraction of this nmscle will press the distal part 

 of the labrum downwards. For the secondary results of the 

 contraction of these muscles, and as to a third pair of muscles 

 (Fig. 17, d; Fig. 21, m-) attached near the base of the above- 

 mentioned apodemes the reader is referred to the section on the 

 internal mouth-organs. 



The Jiypopliarynx (Fig. 16, h) is as long as the labrum ; it is a 

 thin cyHndrical tube, with the apical part membranous (Fig. 19), 

 as in Glossina. ' . ' 



The lahium (Fig. 16, c) differs considerably from that of 

 Glossina. Nearly the whole of the basal half is somewhat 

 swollen, but to a much lesser degree than in the other genus, 

 and its distal portion is considerably less slender ; the dorsal 

 groove is in the distal half proportionately less deep than in 

 Glossina. The labella are slightly higher than the second and 

 than the distal part of the iirst segment ; the labella and the 

 second segment together occupy about one-sixth of the length 

 of the whole organ. The labella have on their outer side near 

 the end, and at the lower margin, a row of partly rather long, 

 partly short setse. The inner side of the labella is exceedingly 

 interesting (Fig. 20). As in Glossina, the plate (c) in the 

 groove is distally very strong, and occupies not only the bottom 

 but the major pai-t of the sides; its end is obliquely truncated, 

 and on each labellum a very high plate (d) is attached to the 

 end by a well-developed articulation. From the basal part of 

 this labellar plate five enormous teeth (e) proceed forwards and 

 downwards. These teeth, which are arranged in a curved row, 

 are firmly anchylosed to the plate, very stout, a little more to a 

 little less than two and a half times longer than broad, distally 

 triangular and subacute. The thz'ee middle ones are distally 

 irregularly serrated along both margins, and possess in addition 

 small secondary processes near one margin ; the upper tooth is 

 serrated distally along the upper and the lower tooth along the 

 lower margin. The area between these teeth and the membranous 

 distal margin of the labellum is occupied by two rows of large, 

 elongate, rather thin and very sharp chitinous blades (/), of 

 about the same shape as the blade of a knife, and directed the 

 same way as' the • large teeth. A little way inside the distal 



