110 STOMOXYS.— PALPI AND PROBOSCIS. 



situated in the bottom of the groove. The ' second pair is veiy 

 large ; each of its muscles terminates in a tendon, which is very 

 strong and runs from the distal end of the inflated portion to 

 the outer wall of the labellum. I am unable to decide whether 

 the slender portion of the first segment of the labium contains a 

 third pair of muscles, like those in Sfomoxjjs, described later on. 



The hypopharynx is firmly united, or one might say fused, 

 with the proximal end of the plate in the groove of the labium, 

 and a little more distally it is connected with the base of the 

 lower wall of the labrum (compare Fig. 22 of Stomoxys). The 

 hypopharynx being a direct prolongation of the posterior wall, 

 and the epipharyngeal plate (the lower side of the labrum) the 

 direct prolongation of the anterior wall of the pharynx, the 

 opening of the mouth may be said to be situated just at the 

 connection between the hypopharynx and the labrum. 



B. External Mouth-parts in Stomoxijs. 



' There is no difference between these organs in the male and 

 f(!male ; furthermore, the differences observed between the 

 mouth-parts in St. calcitrans and the African species are slight. 

 The following description is based essentially on St. calcitrans. 



The proboscis is somewhat longer than the height of the head, 

 horizontally projecting (Fig. 15), but not covered by the palpi, 

 which are very slender, and cylindrical, and in the species 

 examined by me are scarcely one-third or not k quarter as long 

 as the proboscis. This consists of the same parts as in Glossina. 



The labrum (Fig. 16,. a) reaches nearly to the base of the 

 label la. It is more strongly chitinised than in Glossina and 

 almost of the same shape (Fig. 17), but the lateral walls are more 

 incurved below, so that the labrum constitutes a tube with a 

 moderately broad slit along the lower side. The apical portion 

 (Fig. 18) is oblong triangular, subacute, and rather firmly chiti- 

 nised. Not far from the end some sense organs (Fig. 18, s) are 

 observed ; in the sub-basal portion of the labrum such organs ai'c 

 rather numerous, and some are found in the intermediate portion. 

 Each organ bears a moderately short and clear hair, and the 

 ganglion at its base is often easily observed. To each of the 

 lateral basal angles is firmly attached a strong chitinous rod or 

 apodeme (Fig. 17, &), which is rather long and proceeds upwards 

 in the head (Fig. 21, h) ; to its free end is attached a fairly 

 strong muscle, which runs. to th? distal solid end of. the pharynx 



