354 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



While in Alaska I tested some repellents that had been developed 

 since our Hudson Bay trials in 1943. The mosquito species were 

 different, but the repellents proved their value once more, and we were 

 happy. In the Alaska experiments with repellents I allowed each 

 volimteer host to treat one arm himself with only the directions on the 

 container as a guide; then, carefully and throughly, I treated his other 

 arm with the same repellent. Our data show that, on an average, 

 about 30 minutes' additional protection is gained when the chemical 

 is applied by an experienced worker rather than by the untrained host. 



The return trip to the States was by plane over the Alaska Highway 

 from Fairbanks to Great Falls, Mont. En route I stopped for a day 

 or two at each of the several airports and had myself driven in a jeep 

 from 50 to 100 miles up and down the highway in an effort to sample 

 the mosquito population. However, as it was now late in August most 

 of the mosquitoes had died out, so my collections were disappointing. 



DISPER^NG DDT SPRATS WITH LARGE AIRCRAFT 



As the war progressed westward in the Pacific, the need for a 

 modern means of controlling mosquitoes over large areas became 

 urgent. Malaria and dengue were taking a tremendous toll of man- 

 days. DDT, although not proven under practical conditions, showed 

 much promise. Amazing stories from our Orlando laboratory began 

 to appear in 1943 (2) regarding the effectiveness of this new insec- 

 ticide. Under test conditions, at least, a material that could be 

 applied from aircraft was killing mosquitoes and their larvae in a 

 single application (12). Preliminary tests (4) on a small scale in 

 the Florida salt marshes had produced excellent results. Special 

 equipment was soon designed for spraying DDT from various types 

 of aircraft. In April 1944 A. W. Lindquist and W. C. McDuffie (7) 

 demonstrated in Panama the possibility of killing adult mosquitoes 

 in dense jungle with DDT by use of small Navy aircraft equipped with 

 devices designed by C. N. Husman. 



Over large jungle areas these small planes were inadequate because 

 of their small pay loads. We began thinking in terms of large air- 

 craft. Soon an Army project was set up for experimental spraying 

 from a C-47 with a capacity of 800 gallons and a B-25 with a capacity 

 of 550 gallons. Army engineers designed special dispersing equip- 

 ment. The tests were to be conducted over typical jungle in Panama. 



In January 1945, 18 of us flew to Panama from Orlando by way of 

 Texas, Mexico, and Costa Rica in the two Army planes that were to 

 serve as our spraying machines. Together with two four-man Air 

 Forces crews our party included four officers and one enlisted man of 

 the Army, a chgmical engineer from the University of Illinois, and 

 four Department of Agriculture entomologists. 



