CHAPTER II 

 SECTION I 



ANATOMY AND PHYSIOLOGY OF THE BLOOD-SUCKING 



DIPTERA 



THE anatomy and physiology of the blood-sucking arthropods concern 

 the parasitologist in two ways. In the first place, some acquaintance 

 with the external characters by means of which the various forms are 

 separated from one another is essential, in order that the systematic posi- 

 tion of the particular species with which one is concerned may be 

 determined ; the published descriptions of species are written in highly 

 technical language, and without some general knowledge of the structures 

 to which the terms are applied it would be impossible to follow them. 

 Secondly, a good working knowledge of the internal anatomy is indispen- 

 sable in the study of the parasites of insects. Without such knowledge 

 the relations of the parasite to its host, and its possible wanderings in the 

 body of the host, cannot be properly understood. Moreover, unless one 

 knows the relations of the internal structures to one another and to the 

 exo-skeleton, one cannot arrive at a satisfactory method of performing 

 routine dissections. 



In this chapter it is proposed to deal with the Dipterafrom the points 

 of view suggested above, describing the structure and indicating as far as 

 possible the function of the parts. In doing so the general principles of 

 the anatomy and physiology will be explained as occasion arises, in order 

 that, these having once been dealt with, they need not be further referred 

 to in connection with the other blood-sucking insects. The structure of 

 these will be considered under their separate chapters, as they differ too 

 much in their general arrangements to be conveniently considered to- 

 gether with the Diptera. The examples dealt with will be almost entirely 

 blood-sucking flies, and the statements made are not necessarily 

 generalizations for the whole order, unless this is stated or implied. 



As regards textbooks on insect anatomy and physiology, Packard's 

 will be found most useful, though it is now out of date. Berlese's large 



