54 ON THE ANATOMY OF THE FLY. 



it appears upon the back as a dark egg-shaped mass ; it shrivels 

 gradually after the larva ceases to feed, and disappears entirely 

 before the third day of the pupa state ; I shall call it the 

 pharyngeal pouch. 



In the sucking stomach the external or muscular coat consists of 

 interlacing muscular bands, which terminate in pointed, and often in 



DESCRIPTION OF PLATE IV. 



Fig. 1. The alimentary canal, as it appear after the insect has been 

 fed on food mixed with cochineal. The oesophagus and crop are filled 

 with fluid, coloured with the pigment. In the chyle stomach the 

 food assumes a violet colour ; the salivary glands remain uncoloured 

 and present a transparent blueish tint. The bile tubes are only 

 partly shown, with their ducts filled with yellow bile pigment, and 

 the rectal papilla are deeply stained with cochineal. X 12 diam. 



Fig. 2. A portion of one of the false tracheal channels of the pro- 

 boscis ; the protoderm is torn away from the edge of the channel at its 

 right extremity, to show the manner in which it is folded, x 500 diam. 



Fig. 3. A section through a portion of the surface of one of the lobes 

 of the proboscis ; showing a false tracheal channel cut through trans- 

 versely, and the folds of membrane between it and the next channel 

 with one of the nipple-shaped papillae between them, x 500 diam. 



Fig. 4. Side view of the anterior extremity of the chyle stomach ; 

 showing the proventriculus and the sacculated walls of the chyb 

 stomach, x 36 diam. 



Fig. 5. Cylinder epithelium from the chyle stomach, x 250 diam. 



Fig. 6. A portion of the salivary glands, to show the ramification of 

 the tracheal vessels and the disposition of the gland cells, x 250 diam 



Fig. 7. A portion of one of the Malphigian or liver tubes, x 250 

 diam. 



^Fig. 8. The valve between the large intestine and reclnra. x 36 

 diam. 



Fig. 9. A vertical section of one of the rectal papillce or renal 

 organs, x 60 diam. 



Mg. 10. Gland cells from the same, x 250 diam. 



Fig. 11. The apex of the same, x 250 diam. 



Fig. 12. A transverse section of the same, x 60 diam. 



