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



In tills figure the left side of the thornx has been removed, together with the 

 wing muscles and the posterior steruo-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. 



Pig. 16. — Wing. The nervures are drawn slightly thicker than they 

 naturally are. 



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

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

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

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

 2 J/', 21/2. Yvc&i and second second medial cells. 1/1 + 2. Medial longitu- 

 dinal nervure. il/3 + C«. Mcdio-cubital longitudinal nervure. R. Iladial 

 cell. 51 to i2 4+5. Iladial longitudinal nervures. Sc. Subcostal cell. 

 (SVi. Subcosta. 



PLATE 25. 



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

 side. The malpighiau 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 proveutriculus (Pt?.) and ventriculus 

 (Ven:). 



p.itit. Proximal intestine, d.int. Distal intestine, rect. Rectum. 



Fig. is. — Portion of a transverse section of the oral lobes, showing the two 

 types of gustatory sense organ, etc. 



(/.s. Gustatory seta. g.p. Gustatory papilla, hi/. 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. tr. Trachea. 



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

 of the gland cells (^.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 proveutriculus and the anterior end of the 

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

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



Fig. 2], — The posterior region of the alimentary canal, to show the rectal 

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

 (inalp.), 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.) 



