Methods 
The materials were applied to the arms (1/4 teaspoonful elbow to 
wrist) and the legs (3/8 teaspoonful knee to ankle) of the test subjects. 
The treated subjects exposed themselves to mosquitoes in the field to 
determine how long the materials would prevent bites. The time from 
treatment to the first bite was called the repellent time. Most of the 
exposures were continued until more than one bite had been received. 
With some preparations paired tests were made--concurrently on both 
arms or legs of the same subject. The routine procedure was to apply 
each material to several subjects to learn as much as possible of the 
variation to expect on different individuals. No tests were conducted 
against salt-marsh Aedes unless the biting rate was in excess of 20 
bites on an untreated leg in half a minute. The biting rates for the 
mountain Aedes were 5 to 12 per half-minute, for Culiseta 0 to 5, and 
for Mansonia 5 to 10. 
Most of the test materials were liquids, applied undiluted. Some of 
the most effective ones were later diluted with alcohol or used in other 
formulations. In some a thickener such as ethyl cellulose or a powder 
such as bentonite was added to the liquid. In others a pyrethrum insecti- 
cide was included, or two or more repellent materials were mixed. 
Results 
The results of these tests are presented separately for each mosquito 
species. Some of the tables include repellent ratios, calculated by dividing 
the average repellent time of a test material by that of a standard material 
in concurrent tests and then multiplying by 100. The effectiveness of a 
chemical could often be compared best by means of this ratio, as the 
repellent time of any given material varied considerably in different 
test periods. 
Occasionally it was necessary to terminate a test before bites were 
received. Where the repellent time for such a test exceeded the average 
for the completed tests with that material, it was included in the average. 
Such averages are marked in the tables with a plus sign. 
Aedes taeniorhynchus 
Of the 129 undiluted repellents listed in table 1, 21 gaye longer pro- 
tection against taeniorhynchus than the standard material. The following 
materials were 1 1/2 to 2 172 times as effective as the standard: 2-(x- 
chloro-y-ethylphenyl)ethanol; N-butyl-4-cyclohexene-1,2-dicarboximide; 
N-isopentylacetanilide; 1,2,3, 4-tetrahydro-2-naphthol; 2,5,7-trimethyl- 
3-octyne-2,5-diol; and the propyl ester of N,N-diethylsuccinamic acid. 
