_ INTRODUCTION : 23 
trap is inverted and the dead flies shaken down. The living 
flies will go upward and the lid, now on the bottom, is removed 
and the dead flies shaken out. The lid is replaced and the trap 
returned to its normal position without the loss of many live flies. 
Accessory methods and devices. Thorough screening and seal- 
ing of all cracks and other openings through which flies might 
enter living, messing, and other quarters are, of course, a neces- 
sity in keeping flies out of such places. This is particularly true 
of rooms where food is being handled. Poisons, sticky fly papers 
or wires, and other similar devices are of no particular benefit 
in reducing the numbers of blowflies. Blowflies inside buildings 
may be killed by the use of one of the many commercial 5-percent 
DDT-pyrethrum fly sprays or with one of the aerosols containing 
DDT and pyrethrum. It must be remarked in this connection 
that blowflies are more difficult to kill with such sprays than are 
many other kinds of flies. It is usually advisable to sweep up 
those that fall to the floor and dispose of them properly. 
Gutters and sidewalks about market places may be treated 
with a 2.5 percent, water dispersible DDT spray at 15-day inter- 
vals with a resulting remarkable decrease of blowflies about such 
places. 
The residual treatment of inside walls of food-handling estab- 
lishments with DDT is not, however, desirable. Flies affected by 
DDT residual treatments do not die until they have staggered, 
stumbled and bumbled about, often into food. 
Large-scale control methods. Dead men on battlefields and ex- 
crement in latrines produced various species of blowflies in num- 
bers beyond human comprehension on Pacific Islands during 
World War II. This was particularly true in the Marianas during 
July, August, and early September in 1944. The use of DDT, 
eight ounces in one gallon of fuel oil, distributed at the rate of 
two quarts per acre from C-47 type aircraft by the Pacific 
Division Air Transport Command, for the control of a critical 
dengue epidemic on Saipan in September, 1944, brought the 
blowfly situation to a spectacular conclusion. The success of fly 
control programs in the Pacific by this organization was based 
upon a full understanding of fly biology and habits. DDT is an 
effective fly adulticide but is of little value as a larvicide. To 
obtain a reduction in a blowfly population over a long period of 
time, it is necessary to apply the insecticide at 7-day intervals 
for the period of time required by the immature stages to be- 
come adults, the stage of the flies affected. This period is ap- 
proximately 21 days in the tropics during peak breeding activity. 
The area covered was always as great as could be economically 
