MEDICAL ENTOMOLOGY HOWARD. 583 



arthropod of unquestioned pathogenic significance do we now think that we have 

 done with it once for all by a command that its breeding places shall be blotted 

 out, or its natural enemies be let loose upon it. The business of medical ento- 

 mology, as now understood, is, in the case of any species convicted on patho- 

 logical evidence of being a standing danger to the public health, to unriddle its 

 biology in every detail, and to investigate all the varying circumstances that 

 influence its acquisition and retention of pathogenic capacity. The biological 

 inquest must comprehend every stage of the creature's existence, from the egg 

 to the engendering adult, and must include not only its affinities and its struc- 

 ture, but also its bionomy and its relations to environment. The bionomic in- 

 quiry must embrace the geographical distribution and seasonal incidence; the 

 habits and the hours of activity ; the powers and range of locomotion and the 

 propensity to spread ; the food preferences, the meteorological influences, and 

 power of resisting vicissitudes of season and climate; the sexual instincts and 

 fecundity ; the mode of reproduction, breeding places and seasons, and the pro- 

 vision for larvae; and the duration of life in every stage of development. If 

 it be not a specific parasite, the bionomic investigation must also include the 

 relations of the species to its environment, organic and inorganic, such as the 

 physiographical and hydrographical features of the habitat, natural shelters, 

 help givers, parasites, enemies and rivals. An excellent example of the range 

 of the inquiry is furnished by Swynnerton's "Examination of the Tse-tse 

 Problem," published in the Bulletin of Entomological Research for March, 

 1921. (See p. 22.) With the accumulation of exact information on all these 

 points and the rational inferences drawn from it, medical entomology claims to 

 be a science of practical application in preventive medicine — in short, a branch 

 of Hygiene, and a branch which, although it finds its fullest and most constant 

 application in those tropical countries where sanitary arrangements are still 

 crude and imperfect, can not in the mutability of human affairs be neglected 

 in any country. (Tropical Diseases Bulletin, vol. 18, No. 1, 1921, pp. 1-2.) 



In this article we have considered in a far too summary way a 

 dozen of the great discoveries in medical entomology, practically all 

 of them made within the space of 25 years. Even to list the others 

 would fill far more space than can be given here. Scientific labora- 

 tories were teeming with work of this kind down to the outbreak of 

 the Great War in 1914. For the next four years many investigations 

 were stopped. The men working in the sleeping-sickness problem in 

 Africa, for example, had to abandon this work and join the military 

 forces. Men from the laboratories in all the countries at war were 

 sent to the front or to concentration camps to help in the care of the 

 health of the troops. Many a promising investigator was killed. 

 Printing facilities and postal facilities were so hampered that there 

 was almost no news of the progress of investigations sent out from 

 one country to another as in times of peace. None of the scientific 

 men of the allied nations knew for several years what was being done 

 by the trained investigators of the central powers. Nevertheless, the 

 war gave a tremendous impetus to the study of medical entomology. 

 Typhus in the Balkans and in Poland and Russia and in camps con- 

 taining prisoners from those countries, the trench fever which soon 

 developed alarmingly on the western front, and the spread of malaria 



