34 



THE INTERNAL STRUCTURE OF MCSCA DOMESTIC A 



(nit.d.), which innervate the halteres and are the largest pair of 

 thoracic nerves, have their origin from the median dorsal band 

 in front of the metathoraeic ganglia, so that they appear to be 

 almost meeothoracic in origin. The metathorax crural nerves 

 (mt.cr.) arise from the posterior ventral sides of the meta- 

 thoraeic ganglia. Posterior to these a pair of slender nerves, 

 the accessory dorsal metathoraeic nerves, have their origin, and 

 innervate the muscles at the posterior end of the thorax. 



The dorsal band becomes much thinner posterior to the 

 abdominal ganglion, and runs into the abdomen as a median 

 abdominal nerve (ab.n.). In the thorax two pairs of abdominal 

 nerves arise. In the abdomen the abdominal nerves arise alter- 

 nately and irregularly from the median abdominal nerve. The 

 median abdominal nerve finally terminates in the genitalia. 



The Alimentary System (figs. 11 and 12). 



The alimentary canal of the house-fly is shorter than that 

 of the blow-fly, and also than that of Glossina described by 

 Minchin (1905), and slightly longer than the alimentary tract 



oe.- 



FiG. 11. Longitudinal section of the Alimentary Canal of M. domestica. 



ph. Pharyngeal suction pump. oe. Oesophagus, pt. Ptilinum. crj. Supra-oeso- 

 phageal ganglion, s.d. Lingual salivary duct. P]'. Proventriculus. U. Ven- 

 triculus. C. Crop. p.i. Proximal intestine. R. Rectum, r.ijl. Rectal gland. 



of Stomoxys described by TuUoch (1906). It serves as a good 

 example of the Muscid digestive canal. It is of a suctorial 

 character, and consists of pharpix, oesophagus, crop, proventri- 



