12 the external structure of mcsca domestica 



The Skeleton of the Proboscis. 



An account of the proboscis of M. domestica was published 

 by Macloskie in 1880. The proboscis of the blow-fly, which is 

 very similar in many respects to that of the house-fly, has been 

 described by Anthony (1874), Kraepelin (1880) and LowTie (tc). 

 The results of these authors differ in many details. My study 

 of the proboscis of M. domestica confirms Kraepelin's results, 

 and as Lowne's is the only complete account of the muscid 

 head, a full description of the anatomy, both internal and 

 external, of the head of M. domestica will be given. Recently 

 Graham-Smith (1912) has made a very careful study of the 

 anatomy and function of the oral suckers of the blow-fly, Calli- 

 phora erythrocephala. His observations are confirmatory of my 

 -own study of the oral lobes of M. domestica which I made in 

 1906, but which was not described in gi-eat detail in the first 

 part of my monogi-aph (1907). 



Lowne regards the gi'eater part of the proboscis as being- 

 developed from the first maxillae and not from the labium or 

 fused second pair of maxillae. The latter is the usually accepted 

 view, and one which I support on morphological grounds. On 

 account of the very exceptional nature of his conclusion, he refuted 

 the commonly accepted terms of the various parts of the proboscis 

 and invented new ones, an unfortunate habit to which he was 

 addicted. For the sake of descriptive clearness it will be neces- 

 sary to refrain from constant reference to LowTie's terms or any 

 discussion as to theii' merits. 



The proboscis consists of two chief parts ; a proximal mem- 

 branous conical portion, the I'ostrum, and a distal portion which 

 bears the oral lobes and which has been termed the haustellum. 

 The term haustellum has also been used by some authors to 

 designate the distal portion of the proboscis minus the oral 

 lobes. 



The Rostrum (fig. 3). This proximal membranous portion of 

 the proboscis is attached to the edges of the proboscis aperture, 

 that is to the epistomium, genae and the gulo-mental plate. It 

 has the shape of a truncated cone and bears on the anterior side 

 a pair of palps which bear sensory setae of two sizes. 



