PLATE IX 



Figure 1. The labrum-epipharynx of Musca nebula. 



Figure 2. The prestomal teeth and terminations of pseudotracheal 

 channels of Musca convexifrons, Thomson, ch.r., 

 the chitinous strands which surround and support the 

 pseudotracheae at their insertions, and are evidently 

 homologous with the teeth. X 450. 



Figure 3. Two of the prestomal teeth of Musca pattoni, a species 

 allied to the last, and of like habit. Note the 

 difference in the method of termination of the rings of 

 the pseudotrachea. x 600. 



Figure 4. The mentum of Musca nebulo, m., showing the two 

 divisions of the fork, f. and f'., separated by the incision, 

 i., and supporting the furca, from the median portion of 

 which there is a projection, this being closely fused, 

 like the rest of the furca, with the external wall of the 

 labella. x 100. 



Figure 5. A part of the inner wall of the labella of Musca 

 domcstica, showing the three rows of teeth, t., t'., and 

 t"., and the terminations of the pseudotracheae. In all 

 species of Musca examined only the distal portion of 

 the tooth is free from the membrane. After Kraepelin. 



Figure 6. The discal sclerite of Philaeinatomyia insignis, 

 attached to the thickened lateral rods, l.r., which form 

 the margins of the labial gutter. The teeth, as 

 shown in figure 8 on the last plate, are attached by 

 membrane, not by rigid chitin, to the concave distal 

 margin, x 250. 



Figure 7. The proboscis of Pliilaematomyia gurnei, photo- 

 graphed from a cleared preparation. The labrum-epi- 

 pharynx, hypopharynx, and labial gutter are placed in 

 order to the left of the palps. The discal sclerite with 

 the attached teeth is dissected from its attachment to 

 the labial gutter, the labellar wall having been ruptur- 

 ed. Microphotograph by Major Kirkpatrick, I. M. S. 

 X30. 



Figure 8. The anterior wall of the haustellum of Musca nebulo, 

 with the discal sclerite attached. The hypopharynx is 

 partially fused with the thin labial gutter. Note the 

 lateral rods, attached to the discal sclerite in front and 

 fused with the membraneous wall behind. The mem- 

 brane, m., connects the mentum and the labial gutter. 



