MOSQUITO CONTROL TESTS — STAGE 361 



house flies. Horn flies, also, were present in great numbers on all the 

 farm animals. 



I had brought two kinds of DDT with me. A ton of a 50-percent 

 wettable DDT powder was for use as a 2.5-percent water suspension 

 on most of the houses and barns made of thatch and rough lumber 

 and elsewhere on surfaces where the white deposit would not be ob- 

 jectionable. This spray was also used directly on the milk cows and 

 on a few donkeys. Over 90 dogs were dipped in a bath containing 

 1.5-percent DDT. I had brought along also several hundred pounds of 

 technical-grade DDT. This was mixed at the rate of 7 ounces to each 

 gallon of a refined greaseless kerosene of which 22 drums had been 

 brought from the States. Three wheelbarrow sprayers had been 

 shipped from the States, two motor-driven and one operated by hand. 

 A quantity of flat- or broom-type nozzles, oil-resistant rubber hose, 

 and other accessories came in and were ready for use a few days after 

 my own arrival. 



The main problem was to reduce the mosquito population. I had 

 chosen five ways to determine the numbers of mosquitoes before and 

 after treatment. With plans sent to the company several weeks be- 

 fore I left the States, carpenters and mechanics had built three stable 

 traps and a rotary-type trap (1). An extra cone of wire screen had 

 been provided for use on the fender of an automobile. I brought with 

 me a New Jersey light trap. The fifth method was collecting by 

 hand the mosquitoes that landed on two men hired for the purpose. 

 One of these men was a Belgian, an ex-convict from the French penal 

 colony 30 miles distant. The second was a British Indian. The me- 

 chanic assigned to operate the rotary -type trap was a Chinese. These 

 men and those assigned to me for applying the spray were willing 

 and reliable workmen, and to them goes the credit for a big job well 

 done. 



The rotary trap consisted of two cones of screen wire rotated 

 around a pivot driven by a small gasoline engine. The diameter of 

 the cones was such that each screened exactly a cubic foot of air for 

 every foot it was moved forward. The pivot was synchronized to 

 travel at the rate of 20 miles per hour. The two cones were operated 

 about 3 feet and about 5 feet, respectively, above the ground. An 

 identical cone trap was mounted on the fender of our automobile. 

 By driving this car at 20 miles an hour I could screen 52,800 cubic 

 feet in 30 minutes. The two cones, when operated 30 minutes, 

 screened twice as many cubic feet of air but in one spot about 10 feet 

 in diameter. At the small end of each cone I attached a cloth bag 

 having a bottom of fine screening. As the cones moved forward at 

 the rate of 20 miles an hour the cloth bags were stretched out parallel 

 to the cones. At the appointed time each bag was taken off the cone 

 and placed in a jar containing a piece of cotton saturated with chloro- 



