goo THE ANIMAL CARRIERS OF DISEASES 



Weeks bacillus and a spreader of the severe form s^of ^ophthalmia 

 found therein. 



Flies can also carry the plague bacillus in living virulent form in 

 their alimentary canal for forty-eight hours, but they do not play 

 any great part in the dissemination of the disease. 



They also may be regarded with suspicion as spreaders of coccal 

 infections, as these germs have been found in their alimentary tracts, 

 as well as externally. 



Flies are therefore of great importance as intermediary hosts of 

 bacteria, and as such are worthy of study. 



We require to know the house-flies of the tropics, but these are little investi- 

 gated, though Nicholls at St. Lucia has found the following breeding in human 

 faeces; — 



DrosopMla melanogaster Meigen. 

 Limosina punctipennis Wiedemann, 

 Sepsis species. 



Sarcophaga aurifinis Walker. 

 Sarcophaga species. 

 Sarcophagula species. 



In Africa and the East generally:—* 



Pycnosoma war^wa/e Wiedemann. 

 Pycnosoma chloropyga Wiedemann. 



In India by Patton ; — ^1 H 



Musca domestica Linnaeus. 

 Musca domestica var. determinata Walker. 

 Musca nebulo Fabricius. 

 Musca pattoni Austen. 



In England the investigation is much more complete — e.g.:— 



Musca domestica Linnaeus. Fannia scalaris Fabricius. 



Musca corvina Fabricius. Anthomyia radicum. 



Calliphora erythrocephala Meigen. Sarcophaga carnaria Linnaeus, 



Calliphora vomitoria Linnaeus. Sepsis punctum Meigen. 



Lucilia ccBsev Linnaeus. Piophila casei Linnaeus. 



Pollenia rudis Fabricius. Scatophaga stercoria Linnaeus. ^ 



Fannia canicularis Linnaeus. DrosophUa fenestrarum. 



Also Scenopinus fenesiralis and species of Stomoxys and of Psychoda; but 

 these two last have already been described, and now it behoves us to look 

 at the classification and structure of the non-biting flies. 



We have already given the classification of the Diptera in Chapte^ 

 XXXIII., and need only consider that of the families. 



Family Phorid^. 



Phora femorata occurs occasionally in houses. Aphiochceta fevfuginea 

 Brunner causes intestinal myiasis. 



Family Scenopinid^. 



Scenopinus fenesiralis Linnaeus is the so-called window fly, which is prob- 

 ably the only household fly which is not injurious to health. 



