20G Annals Entomological Society of America [Vol. X, 



These notes show that the severity of an epidemic of bubonic 

 plague bears a direct ratio to (a) flea abundance and to (b) humidity. 

 This holds true for India. No doubt it holds true for other 

 places where bubonic plague is endemic. The same set of 

 conditions may not be duplicated elsewhere, but the ecological 

 relations will in the main part correspond to those of India. 



I am indebted to Dr. S. T. Darling, formerly Chief of the 

 Board of Health Laboratory of Ancon Hospital, for the use of 

 his library. 



1903. Gauthier & Raybaud. Revue d' Hygiene, XXV, p. 426. 



1908. Indian Plague Commission. Journ. of Hygiene, Vol. VIII and IX. 



1909. Kitasato. Trans. Bombay Med. Congress, p. 93. 



1910. Tidswell. Rpt. of the Gov. Bur. of Microbiology for 1909 (Sydney) p. 20. 



1910. Jennings. Rats and Fleas in Relation to Bubonic Plague, with Special 

 Reference to Panama and the Canal Zone. Mt. Hope, C. Z. 



