CHAPTER IX 



Insects as Carriers of Disease 



Within comparatively recent years careful study has been given 

 to insects as carriers of human disease, with the result that astounding 

 facts have been disclosed. We know to-day that several of the serious 

 and fatal diseases that afflict man, and several others to which domestic 

 animals are subject, are carried or transmitted by insects ; and in some 

 cases the disease is carried in no other way. The study of these facts 

 and possibilities constitutes the new Medical Entomology. 



House Flies 



Beyond doubt the commonest and the worst offender is the house 

 fly. Both observed facts and careful experiments have proved that 



this insect is instrumental in 

 the spread of typhoid fever, 

 tuberculosis, and certain intes- 

 tinal diseases, and there is every 

 probability that further study 

 wiU reveal others. 



The habits of the fly in its 

 choice of breeding places, its 

 irrespressible tendency to enter 

 our houses and walk over our 

 food, and the structure of its 

 body, especiafly its feet and its 

 tongue, form the chain of circum- 

 stances by which the transfer of disease germs is brought about. The 

 same fly that spent its larval life as a maggot in filth or infected excre- 



42 



Fig. 42. — The House Fly, Musca domes- 

 tica Linn. Enlarged. Original. 



