MYIASES 361 



canal yet many such cases have been connected with the larvae of 

 Sarcophaga carnaria, Calliphora wmitoria and Anthomyia pluvialis. 

 These larvae are usually deposited in the auditory canals of those with 

 otorrhoea. 



The symptoms are intense earache, giddiness and possibly convulsions. The 

 larvae tend to perforate the tympanic membrane. Instillations of 10% chloroform 

 in milk or the use of oils kill the larvse. 



DETERMINATION OF DIPTEROUS LARV.E 



There are certain points in the anatomy of dipterous larvae which 

 must be considered in recognition of the genus or family of the flies con- 

 cerned in the various myiases. The broad extremity is the posterior 

 one and the tapering one the anterior. The dark hooklike processes, 

 which may be in pairs or fused, project from the anterior or head end 

 and above them are a pair of projecting papillae. The second segment 

 from the head has on either side projecting hand or fan-like structures 

 with varying numbers of terminal divisions, 4 to 40 or more. These 

 are the anterior spiracles. 



The large terminal segment has on its posterior surface two chitinized plates with 

 3 slits of various architecture in each. These are the posterior stigmal plates and 

 are the structures we pay particular attention to in identification. In the early 

 larval stages there is only one slit; in the second stage there are two. It is only in 

 the fully developed larval stage that we note the characteristic 3 slit stigmal plates. 

 The presence or absence of a rounded protuberance or button at the base of each 

 stigmal plate should be looked for. The area carrying the stigmal plates may be 

 sunken to form a pit. 



KEY TO LARV2E OF THE MYIASES (BANKS) 



1. Body with lateral and dorsal spinose processes Homalomyia. 



Body without such processes 2 



2. Body ending in two fleshy processes; rather small species 3 



Body truncate or broadly rounded at end 4 



3. Processes bearing the stigmal plates; body about 5 mm. long. . . . Drosophila. 

 Processes not bearing the stigmal plates; body 10 mm. or longer . Piophila. 



4. But one great hook; posterior stigmal plates with winding 



slits; no distinct lateral fusiform areas; tip of body with 



few if any conical processes Muscinae. 



With two great hooks; slits in the stigmal plate not sinuous 5 



5. No tubercles about anal area; no distinct processes around 



stigmal field 6 



Distinct tubercles above anal area; often processes around 



stigmal field; lateral fusiform areas usually distinct 7 



