CHAPTER VII 



Diseases Borne by Non-Biting Flies ^ 

 W. Dwight Pierce 



It will be necessary in discussing the role of flies in the transmission 

 of disease to divide the flies into several categories, because so many 

 species of the order Diptera are involved. The flies cfen be divided 

 into two large groups, those which bite and those which do not bite, 

 but, rather, sip their food. Two excellent monographs on the relations 

 of flies and disease have been published, that on the non-bloodsuckers by 

 Graham-Smith, and that on the bloodsuckers by Hindle. 



This lecture deals with the non-biting flies only. Among these flies 

 are to be found the principal house-visiting flies, foremost among which 

 is the house or typhoid fly, Musca domestica Linnaeus, followed by the 

 blue bottle blow flies, CalUphora vomitoria Linnaeus and C. erythro- 

 cephala Meigen, the green bottle blow fly Lucilia caesar Linnaeus, and 

 various other species. The mouth parts of these flies are constructed 

 only for sucking or sipping liquid or semi-liquid foods. 



In this lecture can only be given a very condensed statement of the 

 relationship of these flies to disease. A more extensive study should, 

 involve the reading of the books by Hewitt and Graham-Smith quoted 

 in the bibliography. In these volumes the evidence is given in great 

 detail. 



Among the most striking of the investigations into the capacity of 

 non-biting flies for the carriage of disease germs, are a series of three- 

 excellent papers by the Italian investigator, Cao, whose work is over- 

 looked by many subsequent writers. In fact, there has been but one 

 good review of his results in English. ■ And yet his investigations opened 

 up the way for practically all of the work on bacterial transmission by 

 insects. Working with larvae and adults of Musca domestica Lwmaeus, 

 CalUphora vomitoria Linnaeus, Luxilia caesar Linnaeus and Sarcophaga, 

 carnaria Linnaeus, he proved that the larvae of these flies could take 

 up and pass through their intestines any bacteria occurring in their 

 food, and that all four species acted exactly alike in this regard. Except 

 where he specifically stated, his results applied to all four species in 



'This lecture was presented in two parts on July 8 and 15 and distributed entire, 

 on July ISj 1918. It has been revised for this edition. 



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