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LUCIUS NICHOLLS — THE TKANSMTSSION OF PATHOGENIC 



numerous ova and larvae of flies had been deposited upon them. In all, twenty- 

 five masses were used and approximately 18,000 flies hatched out, excluding 

 winged and wingless Phoeidae, which formed a later batch ; this gives an 

 average of 720 for each stool. The flies comprised only the following six species, 

 which have been kindly determined by Mr. E. E. Austen, of the Entomological 

 Research Committee. 



Tachinidae. 



Sarcophaga aurifinis, Walk. 

 Sarcophaga sp. inc. 

 Sarcophagula sp. inc. 



Drosophilidae. 



Drosopliila melanog aster, Mg. 

 BORBORIDAE. 



Limosina punctipennis, Wied. 



Sepsidae. 



Sepsis sp. inc. 



The Sepsis was very numerous on all occasions. The Drosopliila does not 



usually breed in this situation ; its larvae can be found in all kinds of fermenting 



or decaying fruit and vegetables. It has some connection with the fermenting of 



cocoa, and during the cocoa crop or the mango season it occurs in large swarms. 



Numbers of them are found in houses in the country, where they settle on 



Fig. 1. — Drosopliila melanogaster, Mg. X 16. 



all forms of food or drink, and they are also found swarming round latrines in 

 search of undigested vegetable matter. The Limosina is by far the most 

 objectionable of them all, as on every occasion on which it was caught its 

 abdomen was found to be distended with pure faecal matter. In 26 out of 100 

 specimens, taken in different situations, I have obtained the ova of the worms, 

 Ascaris lumbricoides, Necator americanus, or Trichoceplialus dispar. 



All the above three species lay eggs which they force into the faecal matter, 

 two prolongations of the egg-covering alone protruding. The larval period is 

 short and followed by a longer pupal period. 



All the Tachinids deposit comparatively large living larvae, which immediately 

 crawl into the mass ; again the pupal period is longer than the larval. In 15 

 pregnant females of the Sarcophagula dissected, the lowest number of larvae 

 found was eight and the highest 21. 



