98 PROC. ENT. SOC. WASH., VOL. 20, NO. 5, MAY, 1918 



workers have added corroborative evidence to 'Cao's findings, 

 although certain of the pathogenic "bacteria have been found by 

 Ledingham, Bacot, Tebbutt, and others to pass with difficulty 

 through insects in the presence of large colonies of normal fly 

 bacteria. 



Climate and Life 



One very interesting phase of the whole subject is the emphasis 

 placed by author after author on temperature conditions affecting 

 the organism, or the insect, or its host. And yet the majority of 

 these investigators while stumbling on important biological laws 

 show a lack of understanding of certain fundamental principles. 

 Seldom, if ever, is there any mention of humidity, which bears as 

 strong a relationship to life as does temperature. In fact the 

 numerous records of failure to keep insects alive during the exper- 

 mental work cause a suspicion that the humidity factor in the 

 breeding cages was overlooked. The bacteriologists recognize 

 high and low fatal temperatures, high and low sluggish periods, 

 and a temperature of most favorable growth, which we know as 

 the optimum temperature'. Among the protozoologists these 

 zones of temperature are not worked out so clearly. Nowhere 

 have I seen a recognition of the fatal, sluggish and optimum zones 

 of humidity. I am convinced that in many cases certain confusion 

 which has arisen among various workers will be cleared up by a 

 correlation of the humidity and temperature environment in 

 which they worked. Apparent discrepancies will disappear 

 entirely with this correlation. 



Possibility of Error 



Many errors have crept into the literature through the efforts 

 of a zealous investigator to go beyond the bounds of his training. 

 Entomologists have been guilty of trying to conduct transmission 

 experiments without understanding the organism they were 

 transmitting, or possibly without knowing the normal insect 

 parasites. Parasitologists have frequently made mistakes in 

 their work through misunderstanding the insects they were 

 dealing with. The subject is large, demanding tremendous patience 

 and care, and there are many possibilities of misunderstanding 

 results. 



We will now pass to the medical and veterinary side of the 

 question. 



THE MEDICAL PHASE OF THE SUBJECT 



My introduction has been long because on the biological work 

 is built the whole fabric of medical entomology. As I am looking 



