(48) 



442 0. GORDON HEWITT. 



distended by the action of inflated air cannot be held. The 

 extension of the proboscis I believe is due to the inflation of 

 the tracheal sacs of the head and rostrum, and I agree with 

 Kraepelin that the distension of the oral lobes is effected by 

 blood-pressure. 



Two kinds of gustatory sense-organs are found on the 

 margin of the aboral and on the oral surfaces respectively. 

 The latter were described in the blowfly by Lowue as the 

 openings of the ducts of the labial salivary glands, but 

 Kraepelin's correct description of their structure in the 

 blowfly is confirmed by this study of the House-fly. The 

 labial salivary glands are described in detail. They consist 

 of large cells containing permanent vacuoles, which com- 

 municated with intracellular ducts. These open by a pair of 

 pores into the oral pits, the secretions of the glands serving 

 to keep the surface of the oral lobes moist. 



VII. LITERATURE. 



The following is not intended to be a full list of the litera- 

 ture relating to M. domestic a. Further references will be 

 given in the succeeding parts. 



1824. ANDOCTIN, V. " Recherches Anatomiques sur le thorax des Animaux 



Articules et celui des Insectes Hexapodes en particuliere," 'Ann. 



Sci. Nat. Zool.,' vol. i. 

 1906. AUSTEN, E. E. ' Illustrations of British Blood-sucking Flies,' 74 pp., 



34 col. plates. Brit. Mus. (Nat. Hist.), London. 

 1902. BERLESE, A. "L'accoppiamento della Mosca domestica," 'Rev. 



Patolog. vegetale,' vol. ix, pp. 345357, 12 figs. 

 1834. BOUCHE, P. FR. ' Naturgeschichte der Insekten,' Berlin. 

 1898. COMSTOCK, J. H., and NEEDHAM, J. G. -"The Wings of Insects," 



'Amer. Nat.,' vol. xxxii, p. 43, etc., and through the vol. into 



vol. xxxiii. 

 1752-78. DE GEEK,, CARL. 'Memoires pour servir a 1'Histoire des Insectes,' 



Stockholm. 

 1881. HAMMOND, A. "On the Thorax of the Blowfly (Musca vomi- 



toria)," ' Journ. Linn. Soc,' (Zool.), vol. xv, pp. 9 31, 2 pis. 



