56 THE EEPORT OF THE No. 36 



within the protected districts. This public approval will continue for two or three 

 or even more years, and the occasional appearance of a troublesome number will be 

 discounted. 



But as time passes the remembrance of the suffering experienced before any 

 work was done will fade, and the appearance of the occasional outbreaks will be 

 charged to inefficient work on the part of the mosquito control organization, and 

 the appropriations necessary for the support of the work may be discontinued. The 

 public will demand that freedom each year become noticeably greater. Of course, 

 this natural change of public opinion may be delayed by educational work in the 

 course of which the nature of the problem is explained. But sooner or later the 

 public will demand that even this occasional trouble, this apparently irreduceable 

 minimum, be eliminated. 



Without doubt methods not now in use must be developed if this demand is 

 met. A more fundamental study of the mosquito's natural history must be made 

 in the hope that a clue to the accomplishment of further reductions may be found. 

 The chemotactic responses of this insect are practically unknown. The develop- 

 ment of larvicidal agents has only begun. There is much room for that type of 

 research which will develop new and better methods of getting at the problem of 

 mosquito control. 



Evaluation of the Eesults of Mosquito Control. 



The last phase of the problem of mosquito control is the evaluation of the- 

 resultai of anti-mosquito work. In dealing with the species which disseminate well 

 known and definitely diagnosed diseases this phase seems to offer little difficulty. 

 Before the work is done a survey of the number of well authenticated cases of 

 disease should be made. Each year after the work the survey is repeated and the 

 conditions before and after compared. This is well illustrated in the work at 

 Princeton, where in. 1914 before the work of control began there were 127 cases of 

 malaria, while in 1915, after the work had made a good start, there were 65 cases, 

 and in 1916, after the large part of the work had been done, there were 8 cases. 

 Still more striking results were presented by Dr. Carter last winter. At Eoanoke 

 Eapids, North Carolina, in several mill villages of over 4,000 total population, anti- 

 mosquito work reduced the physicians' calls from 50 per day to 21/0 per day the first 

 year, and to one call for each three days the second. At Wilson, Virginia, in 1915, 

 every house visited -by Dr. Carter had at least one inmate sick with malaria. The 

 five deaths which occurred in August may be taken to indicate that there were 

 about 500 cases in the place. In the summer season following efficient anti- 

 mosquito work there was only one case. 



Thus far the only ways of measuring the value of anti-mosquito work when 

 only the comfort of the people is served, are public approval as voiced by the 

 newspapers and governing bodies, and the advancement in valuation of property 

 for taxing purposes. 



The first usually appears in a form similar to the following taken from the 

 Newark ^i;eniw/7 Star on August 16, 1912: 



" That the work of mosquito extermination in Essex County this season has been 

 well done, nobody can doubt or deny. The pest ^vas not entirely destroyed, but that was 

 not expected. The mosquito extermination Act has been amply justified by results and 

 its repeal by the legislature at the demand of some parsimonious county that is willing 

 to suffer the pest rather than (pay the small price for getting rid of it is impossible." 



