2 - 



Usually 10 chemicals were tested at a time . A mosquito repellent 

 containing 60 percent of dimethyl phthalate^ 20 percent of Indalone, and 

 20 percent of 2-ethyl-l,3-hexanediol was included in each series of tests 

 for comparison. This mixture, known as M-250, was developed by the Bureau 

 of Entomologj^ and Plant Quarantine and was used by the Armed Forces dviring 

 World War II. An acetone -sprayed mouse was used as a check with each 

 series. It was found that the flies would usually bite check mice within 

 10 minutes. 



Ihiring exposxare of the mice to the flies, constant observations were 

 made for landing and biting. As soon as a definite bite was observed, the 

 test was terminated. If a bite was not obtained in h'^ to 60 minutes, the 

 test was stopped for 1 hour or longer, and then the mouse was exposed to 

 other flies. This procedure was continued until a bite was obtained or 

 the test was terminated owing to the lateness of the hour. For this reason 

 the repellent times eire not always precise. Some chemicals caused a rapid 

 retreat of the fly when it touched the treated mouse; others had little 

 effect. Fumigation may have been a factor with some of the chemicals that 

 gave long protection times. The best compounds from several series were 

 usually retested. 



This method of testing eliminated many materials on the basis of one 

 test. Promising compounds were subjected to further tests. Some of the 

 materials that repelled flies for 200 minutes or more in the first test 

 failed to protect for a similar period when retested. 



In the accompanying lists are included 153 chemdcals that repelled 

 deer flies for less than 125 minutes; 8o chemicals that gave repellent 

 times of 125 to 225 minutes, several, of which were tested twice; and 2k 

 materials that repelled for more than 225 minutes. The standard repellent 

 M-250 gave average protection times of 133 and 11^4- minutes in tests con- 

 ducted in 194-9 and I95O, respectively. 2-Amino-3-isobornyloxy-2-methyl- 

 1-propanol (O-i+265) and Santomerse DT (0-l6k-dk) were consistently more 

 effective than the other materials, the average protection times being 

 783 and 1,926, respectively. 



Field Tests 



Five of the materials that showed prom.ise in the laboratory were 

 tested on calves. Various pyrethrum and allethrin sprays were also 

 tested. The materials were applied undiluted with a small hand sprayer 

 at the rate of 10 ml. per calf. Effectiveness was determined by counting 

 the tabanids on treated and untreated animals from 2 to 5 times per day. 

 Unless otherwise stated, all observations refer to discalis. 



2-Amino-3-isobornyloxy-2-methyl-l-propanol prevented biting for 1 to 

 3-1/2 days, and Santomerse DT for 1-1/2 to 2-1/2 days. They were the best 

 materials tested. Scintomerse DP remained in the hair for several days 

 as evidenced by the lather caused when a few drops of water were rubbed 

 on the animal. However, it was the most injurious material tested 

 causing the hair to come out. 



