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An application of 4 ml. of this spray per square foot remains effec- 
tive for 3 to 5 months.— U. S. Publio Health Service (354). 
A 3-percent DDT dust had little effect against adults hut as 
little as 0.6 percent of DDT in kerosene kept tents free of adult6 
for the 3 l/2-week test period. DDT-oil emulsion destroyed the orig- 
inal mosquito population in the treated area, but mosquitoes coming 
into the area were able to bite. Therefore, DDT is not efficient foi 
temporary outdoor protection. Field and laboratory tests were made 
against larvae of Culex pipiens , Aedes sollioitans , and Anopheles 
quadrimaculatus with dusts, emulsions, alcoholic colloidal dispersions, 
and kerosene solutions. The dust diluents used were talc and pyro- 
phyllite. The most used emulsion (50-D) contained 66 percent of kero- 
sene, 2 percent of DDT, 0.6 percent of sodium lauryl sulfate, and the 
rest water, and was diluted 1 to 10 with water for field application. 
— N. J. Agr. Bxpt. Sta. (275) . 
A new device for mosquito extermination oonsists of a bottle con- 
taining a small amount of TJOT in oil, which is partly buried in the soil 
where hatching is likely. The bottle has an opening just above ground 
level. When the flood water arises to this opening, the oil floats out 
and spreads a thin, deadly film to kill newly hatched mosquitoes as 
they come to the surface.— St ener son (337 ). 
Tests against adults were made in a Peet-Grady chamber using 6 ml. 
of spray and a 2 l/2-minute exposure. The laboratory tests showed that 
1 percent of DDT in deodorised kerosene gave only a 57 percent knock- 
down but a 24-hour mortality of 100 percent. A 1-percent Pyrethrol 20 
spray gave excellent knock-down (97 percent) and kill (94 percent). One 
percent of a 20*peroent DDT and 80-percent Thanite combination gave re- 
sults which compared closely with the pyrethrum, namely, 92 percent 
knock-down and 96 percent kill; whereas the corresponding results for a 
spray made up of 1 percent of a 40-pereent DDT and 60-percent Thanite 
combination were 86 peroent knock-down and 99 percent kill. The poor 
knock-down produced by DDT alone in -fee laboratory led the investigators 
to restrict field tests to combinations of DDT and Thanite, using py- 
rethrum as a standard spray for comparison. The results obtained from 
nine replications were as follows! 1.5 percent Pyrethrol 20, 88 peroent 
knook-down and 73 percent kill; 1«5 peroent of the 20-peroent IDT and 
80-peroent Thanite combination, 86 peroent knock-down and 94 peroent 
kill; 1.5 peroent of ttie 40-percent DDT and 60-percent Thanite combi- 
nation, 84 percent knock-down and 98 percent kill. Both the DDT-Thanite 
•prays gave good results, but the 20-80 combination appears to be 
particularly promising.— Rioe et al. (301) • 
