VI 11 PREFACE 



in all the continents has necessitated the preparation of a com- 

 pletely new work. I have naturally endeavoured to review what- 

 ever work relating to the house-fly has been carried on, but it is 

 not unlikely, in fact, with the multiplicity of scientific journals, 

 most probable that some contributions to our knowledge may 

 have escaped my notice and any advice in regard to such omis- 

 sions would be most cordially appreciated. 



The volume is not intended as a popular treatise on the 

 subject. Such a function is filled by my small volume " House- 

 flies and how they Spread Disease " in the Cambridge Manuals of 

 Science and Literature, and by Dr L. O. Howard's book "The 

 House-fly : Disease Carrier." It is primarily intended for the use 

 of entomologists, medical men, health officers and others similarly 

 engaged or interested in the subject, and it is hoped that it will 

 be of value to students. 



I w^ish to acknowledge my indebtedness to Mr H. T. Giissow, 

 who took the photographs illustrated in figs. 33, 72, 74, and to 

 Mr C. T. Brues, of Harvard University, for the use of the original 

 photograph, fig. 36. Mr F. W. L. Sladen also has kindly assisted 

 me by taking the photographs, figs. 32, 35, 70, 97. Except where 

 it is otherwise stated, the rest of the illustrations were drawn 

 by me. 



C. GORDON HEWITT. 



Ottawa, Canada, 

 July, 1913. 



