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of f lies all summer with two applications of 18 gall cms each of a 2-per- 
cant suspension of Neooid A-20#— Hodson (212 ) » 
Adult houseflies of both sexes, 5 days old, were sprayed under 
regular Peet-Grady test conditions with 0.2 percent of DDT in Deobase. 
DDT caused slight dissolution of fiber tracts and degeneration of nuclei 
both in the brain and in the fused thoracic ganglia, but in spite of its 
pronounced neurologic symptoms histological changes were relatively 
slight.— Hartzell (202) . 
Five percent of DDT in kerosene painted on a fly screen killed flies 
for more than 6 weeks. Where the sun shines on the screen it will last 
for 2 or 3 weeks. — Hutson ( 220 ) . 
DDT is a contact poison to Fu s ca domestica . — Domenjoz ( 135 ) • 
Preliminary tests were made of DDT in a solvent composed of 90 
percent acetone and 10 percent Deobase by applying the spray directly 
to screen cages containing the flies. From the dosage-mortality curve 
so obtained, it was found that dilutions as low as 0.025 percent were 
quite effective against flies with regard to kill but were slow in 
knockdown. Sprays ranging from 5 percent to 0.2 percent of DDT gave 
complete knockdown in from 11 to 15 minutes. It was clear that DDT 
was slow in knockdown and that its knockdown could not be increased ma- 
terially by an increase in concentration of the DDT. On the basis of 
these results, three Deobase sprays were made up containing 0.2 percent 
of DDT to give a safe margin for practical use. Each spray contained 
a different paralytic agent to evaluate three common agent3 now on the 
market. Butyl carbitol thiooyanate was used at 0.75, bornyl thio- 
cyanoacetate at 1.2, and pyrethrins at 0.05 g. per 100 ml. of spray. 
These sprays were evaluated in the Peet-Grady chamber and in labora- 
tory rooms in which 300-500 flies had been liberated. The sprays were 
found to be almost equally effective, killing all the flies overnight. 
In the practical tests in rooms, knockdown required about 30 minutes, 
probably because of the high ceiling in the rooms used. Knockdown in 
the Peet-Grady chamber was very satisfactory in each case. A Deobase 
spray containing 0.2 percent of DDT was atomised into a Peet-Grady 
chamber at the rate of a fluid ounce per 1,000 cubic feet. Sheets of 
cellophane and cotton towels were placed on the floor of the chamber 
to catch the falling residue, and, after all the spray had settled 
out, the oellophane towels were removed and placed in glass cages 
containing about 100 flies each. The residue from a single spraying 
on oellophane (0.33 mg. per sq. ft.) killed 74 percent of the flies 
confined with it for 24 hours. Sheets held for 7 days before exposure 
to flies killed only 1 percent of the insects. Tie residue from three 
sprayings (l mg. per sq. ft.) killed 100 percent and 88 percent of the 
LIBRARY 
STATE PLANT BOARD 
