(53) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 447 



In this figure the left side of the thorax has been removed, together with the 

 wing muscles and the posterior sterno-dorsales. It must be imagined that 

 this figure is superimposed on Fig. 13. 



do. Dorsales. l.th.s. Lateral thoracic sac. m.v.s. Median ventral sac. 

 n.th. Posterior thoracic spiracle, sc.s. Scutellar sac. st.do. Sterno-dorsales. 



FIG. 16. Wing. The nervures are drawn slightly thicker than they 

 naturally are. 



an. Anal lobe. al. Alula, as. Antisquama. A. Anal cell. A v Anal 

 nervure. Cu. Cubital cell. 1 Cu. First cubital cell. cu-a. Cubito-anal trans- 

 verse nervure. C v Costa. C. Costal cell. 1 C. First costal cell. M. Medial 

 cell. m.cu. Medio-cubital transverse nervure. m. Medial transverse nervure. 

 2 M l , 2 If 2 . First and second second medial cells. Jfl-f-2. Medial longitu- 

 dinal nervure. M3 + Cu. Medio-cubital longitudinal nervure. R. Radial 

 cell. E\ to 224+5. Radial longitudinal nervures. Sc. Subcostal cell. 

 Sc. Subcosta. 



PLATE 25. 



FIG. 17. The alimentary canal as it is seen on dissection from the dorsal 

 side. The malpighian tubes have been omitted, and also the distal portion of 

 the lingual salivary gland (s.lg.') of the right side. The duct of the crop (Cr.) 

 is shown by the dotted line beneath the proventriculus (Pv.) and ventriculus 

 (Fen.). 



p.int. Proximal intestine, d.int. Distal intestine, reef. Rectum. 



FIG. 18. Portion of a transverse section of the oral lobes, showing the two 

 types of gustatory sense organ, etc. 



g.s. Gustatory seta. g.p. Gustatory papilla, hy. Hypodermis under which 

 lies a pigmented layer, p.s. Pseudo-trachea in section, s.g.p. Sensory bulb 

 of gustatory papilla, sp. Sensory bulb of gustatory seta. .lr. Trachea. 



FIG. 19. Transverse section of labial salivary gland, to show the structure 

 of the gland cells (g.c.). (Camera lucida drawing.) 



hy. Hypodermis. ic.d. Intracellular duct. p.s. Pseudo-trachea, od. 

 Opening of intracellular duct into the permanent vacuole (vac.} of the gland 

 cell. 



FIG. 20. Section through the proventriculus and the anterior end of the 

 ventriculus, to show the structure of the proventricular plug (Pv.p.) and the 

 ducts of the oesophagus (ces.) and crop (d.cr.). (Camera lucida drawing.) 



FIG. 21. The posterior region of the alimentary canal, to show the rectal 

 glands (rect.gl.) with their tracheal supply, the origin of the malpighian tubes 

 (malp.), and the position of the rectal valve indicated at X . 



FIG. 22. Transverse section of the lingual salivary gland, showing the 

 fibrillar character of the gland cells, x 220. (Camera lucida drawing.) 



