440 C. GORDON HEWITT. 



generally employed by dipterologists to the morpliological 

 divisions of the insect head capsule are shown. On morpho- 

 logical grounds, the view that the distal portion of the 

 proboscis represents the modified second masillte or labium 

 is adopted, as opposed to that of a first maxillar derivation 

 put forward by Lowne for the blowfly. 



2. After a detailed description of the external and in- 

 ternal skeletal structures of the thorax, the neuration of the 

 wings is described in the terms proposed by Comstock and 

 Needham in their valuable memoir; and to facilitate their 

 more general adoption for the wings of the Muscidfe and 

 other Diptera, a comparison is made between their nomen- 

 clature and the several systems employed in describing the 

 muscid wing. 



3. The abdomen is shown to consist of eight segments in 

 the male and nine in the female, in both cases the first five 

 segments form the visible portion of the abdomen ; the 

 external genitalia of the two sexes are described under 

 another section. 



4. As the muscular system does not differ from that of 

 Volucella described by Kunckel d'Herculais and the blow- 

 fly described by Hammond and Lowne, it is briefly described. 

 The cephalic muscles, however, are fully described in the 

 detailed description of the head (V). 



5. The nervous system, which is of the normal muscid type, 

 is described, but for the sake of clearness a very detailed 

 description of the composition of the cephalic ganglion is not 

 given. The structure of the optic tract is similar to that of 

 the blowfly as described by Hickson. The structure of the 

 thoracic nerve-centre is found to differ slightly from that of 

 the blowfly as described by Lowne. 



6. The alimentary canal is similar in its structui*e to those 

 of Stomoxys and Glossina, only differing in a few details. 

 The mesenteric region, which is represented by the ventri- 

 culus or chyle, stomach, and proximal intestine, is well 

 developed. The lingual salivary glands, rectal glands, and 



