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flies in the 1- and 7-day intervals after spraying. Six spray applica- 
tions (2 mg. per sq. ft.) produced a residue killing ail flies even 
after the 7-day interval. From these results it is quite evident that 
fly sprays containing 0.2 percent of DDT will leave a toxic residue 
when they settle out on nonabsorbent surfaces near or on the floor of 
a room. Spray residues on cotton towels were much less effective against 
flies. Six spray applications (2 mg. per sq. ft.) killed only 46 per- 
cent of the flies confined on the towels within the first day after 
spraying. Eighteen application (6 mg. per sq. ft.) killed 92 percent 
of the flies on immediate exposure and 89 percent 7 days after the spray 
was applied. These figures show that several applications of a fly 
spray containing DDT in a room will leave a toxic residue on nonporous 
surfaces on which it settles, but that toxic residues will not be 
built up on porous materials such as carpets, bedspreads, etc Several 
different types of DDT formulations were applied to nonabsorbent sur- 
faces to check the type of residue likely to be most effective against 
houseflies. In order of their effectiveneas, these compositions were 
a DDT solution in a nondrying oil, a 5-peroent dust (talc), an aqueous 
suspension of a wettable powder, a solution in acetone, and a 5-peroent 
solution in paste wax. The results seem to indicate that residues are 
effective in proportion to their ease of removal or low adhesivity to 
surfaces.-- Goddin and Swingle (179 ) . 
One percent of DDT in kaolin was dusted on sheets of paper on which 
insects were placed separately and covered with a beaker. The time in 
minutes, to partial paralysis was 6, to total paralysis 20, and to 
death 150-160.— Sen (311). 
The effect of a residual deposit of DDT on flies was investigated 
under practical conditions at the Central Experimental Farm, Ottawa, 
from September 7 to November 14, 1944. GNB-A-DDT (commercially pure 
DDT) was dissolved in a small quantity of benzene and diluted to 5, 4 
and 3 percent with deodorized kero. ^ne. Walls and ceilings were spray- 
ed in (a) a milk room with 5 percent spray, (b) a dairy building with 
4 percent, (c) a calf barn with 3 percent, and (d) a piggery with 3 
percent. Control during the period of almost 10 weeks averaged 99 per- 
cent in the dairy, 96 percent in the piggery, 92 percent in the milk 
room, and 88 percent in the calf barn. The daily kill at one time 
reached approximately 30,000 in the piggery. The tests were terminat- 
ed by cold weather. Flies killed included Musca domestica L», St om oxys 
calcitrans L., Fannia canicularis L., Lu cilia caesar L., Vuscina 
stabulans Fall., and" a few other species in small numbers.— Ross (306 ) . 
Musoina stabulans (Fall.), the false stablefly 
Same as for Musoa domesti ca.— Ross (306 ) • 
bxphona irritans (L.), the hornfly 
See Musca domestica.— Anon. (49); Munro et al. (271) . 
