658 



A STUDY OF THE EXTERNAL BREATHING-APPA 

 RATU8 OF THE LARV^ OF SOME MUSCOID 

 FLTES. 



By John L. Froggatt, B.Sc. 



(Plate Ixx.) 



Heretofore, in the identification of different species of liies 

 from maggots collected, the perfect flies have had to be bred-oiit. 

 But, in the course of the work of the Government 8heep-Fly 

 Experiment Station, this method was often impossible, when 

 packets of maggots were received dead or rotten. By means of 

 the microscope, I have found that an examination of the spiracles, 

 in particular the posterior spiracles, gives a sure and certain 

 means of identifying the different species here dealt with. As 

 their description has not been published heretofore, the results 

 are here recorded. In every case, the tj'pes were procured from 

 eggs deposited by each species of fly, on meat in the field - 

 laboratory. 



The species dealt with in this paper are: — 



Anastellorhina augur {Calliphora oceanuf^). 



Pollenia stygia {Calliphora villosa). 



Pycnoso7na rufifacies {Calliphora rujifacies). 



Pycnosoma varipes (Calliphora raripes). 



Lucilia sericata. 



Ophyra nigra. 

 The spiracles, in all probability, exercise a most important 

 function in the destruction of maggots by poison. Careful ex- 

 amination of the skin does not reveal the presence of any pores; 

 the organs of the maggot may be looked upon as being enclosed 

 in an india-rubber-bag, the only openings into which are the 

 cfuUet and anus — the extremities of the alimentary tract — and 

 the anterior and posterior spiracles— the extremities of the 

 respiratory system. These anterior and posterior spiracles are 

 connected by two main tracheae, from which branches ramify 



