FIG. i. 



THE HOUSE FLY (Musca doincstica). This fly is now known to be 

 the principal carrier of the microbes of infectious diseases to man. 



(This picture is from a model by Mr. Ignaz Matausch in the American 

 Museum of Natural History. Every part of the fly was modelled exactly to 

 scale, and it was the product of nearly a year s work.) 



