DISPERSAL OF PARASITIC EGGS 209 



which it was caught its abdomen was found to be distended with 

 pure faecal matter." " In 26 out of lOO specimens, taken in different 

 situations," he obtained the ova of the worms A scan's Imnbricoides, 

 Necator americamis, or Trichocephabis dispar. 



Summary. 



It is evident from the investigations which have been quoted 

 that house-flies and other species are greatly attracted to the 

 ova of parasitic worms contained in faeces and other materials, 

 and make great efforts to ingest them. Unless the ova are too 

 large they often succeed, and the eggs are deposited uninjured 

 in their faeces, in some cases up to the third day at least. The 

 eggs may also be carried on their legs or bodies. Under suitable 

 conditions food and fluids may be contaminated with the eggs of 

 various parasitic worms by flies, and in one case infection of the 

 human subject has been observed. Faeces containing tape-worm 

 segments may continue to be a source of infection for as long as 

 a fortnight. Up to the present, however, there is no evidence 

 to show what part flies play in the dissemination of parasitic 

 worms under natural conditions. 



CHAPTER XXI 



INFECTION BY NON-BITING FLIES OF THE WOUNDS 

 CAUSED BY BITING FLIES 



Patton seems to have been the first to recognize that the 

 wounds produced by biting flies might be infected subsequently 

 through the agency of non-biting flies. His observations relate 

 to a species of Indian Musca, named by Austen (1910) 

 M. patt07ii. " This fly has peculiar habits, in that it sucks the 

 blood which oozes from the bites inflicted on cattle by 

 HcEmatopota, and other Tabanids, Stomoxys, and PJiil(£matoniyia. 

 It likewise sucks the juice out of vaccine vesicles of calves, and 

 also the blood after the vesicles are scraped. The species 

 breeds in cow dung and its pupae are dirty zvhite.'" 



G.-s. 14 



