PROCEKDINGS 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. II, pp. 541-604. December 28, 1900. 



A CONTRIBUTION TO THE STUDY OF THE IN- 

 SECT FAUNA OF HUMAN EXCREMENT. 



[WITH ESPECIAIv REFERENCE TO THE SPREAD OF TYPHOID 



FEVER BY FLIES.] 



By L. O. Howard, Ph.D. 



[Plates XXX, XXXI, Figs. 17-38.] 



CONTENTS : 



lutroductory 541 



General Results of Investigation 547 



List of Diptera Reared or Captured 548 



Insects other than Flies found on Excrement 555 



Details Concerning the Excrement Flies Studied 557 



INTRODUCTORY. 



In 1895 the writer became interested in the study of the com- 

 mon house fly {^Musca doniestica) . Breeding-cage experiments 

 described with some detail later on in this paper early convinced 

 him that horse manure is the favorite food of this species. Even 

 in the presence of kitchen garbage, cow dung, and human ex- 

 crement, flies in confinement oviposited exclusively on horse 

 manure. In the absence of the latter substance but in the pres- 

 ence of the others, he noted egg-laying on decaying fruit and 

 on cow dung but the resultant larvae failed to develop. He con- 

 sidered himself warranted in the statement that probably 95 

 percent of the flies found in cities come from the piles of horse 

 manure everywhere so prevalent, especially in the vicinity of 

 stables. 



After the outbreak of the war with Spain, in the spring of 

 1898, a mild form of typhoid fever soon became prevalent in 

 Proc. Wash. Acad. Sci., December 1900. ( 54i ) 



