DIPTEROUS ENEMIES OF MAN. 27 



sion, such have been added, made from original studies of 

 the natural object during tlie past four months. Where 

 any of these illustrations are taken from tlie works of 

 other authors, credit will be given on the leaf facing the 

 plate. 



Equally important to a- clear understanding of this en- 

 tire discussion is a knowledge of the literature on the 

 subject. A bibliography of this sort will be found in 

 the appendix, with the method of its selection fullv ex- 

 plained. The system of reference numbers used is prob- 

 ably the most convenient attainable. A full reference 

 in parenthesis each time an authority is quoted is cum- 

 bersome, and foot notes are more or less distracting to tlie 

 attention ; consequently the bibliographical list has been 

 arranged alphabetically by authors or journals, and chron- 

 ologically under each heading. These separate references 

 have been numbered consecutiv^ely, and these numbers fol- 

 low an authority when quoted. 



