rosea Ue BON Ris Dee lel N 3 
much turbidity in interior lakes and ponds as to influence aquatic plant 
growth. 
The ponds in the vicinity of headquarters were more open, and one 
near the entrance highway more nearly represented a prairie pond with 
a good population of amphibians. While most of the spray fell on wood- 
lands, a few ponds typical of open marshes gave some indication of what 
might happen to marsh fauna. 
APPLICATION OF DDT By AIRPLANE 
On August 8, spraying began with a B-25 Mitchell bomber using 
No. 2 fuel oil as a spreader and solvent in a 5 per cent DDT solution 
and emulsion, at 10:55 a.m. down river from Bellevue Dam. The plane 
flew at elevations from 100 to 200 feet, traveling at 200 miles per hour, 
and through a pipe in the bomb bay door released the spray at the rate 
of 210 gallons per minute. Tanks in the plane holding 550 gallons were 
refilled at Truax Field, Madison, Wisconsin. In the August-September 
sprayings, strips were made from 300 to 400 feet wide, depending on the 
air currents, and were guided by an Army jeep spaced by Dr. Searls at 
intervals along the Bellevue Dam and on the highway leading to the 
Depot headquarters. This ground control was highly important, as it 
permitted little overlapping and a uniform coverage. Checks made with 
yellow paper spaced at 50-foot intervals and examination of the rubber 
expansion cracks on the concrete highway bore this out. The October 
spraying was done entirely by pilot control from the air, and as a result, 
several areas were treated 2 and 3 times, while others were missed. It is 
uniform coverage at the rate planned that minimizes the harm to fish 
and wildlife. Sprayings were approximately at 30-day intervals. 
METHOD OF STUDY 
Populations of birds and mammals were determined as nearly as a 
hasty inventory would permit before and after each of the sprayings. 
It was assumed that the lists for August and early September represented 
the resident bird populations, while the October lists were confined to those 
known to have not been affected as yet by migration through the area. 
Fourteen mosquito checking stations on the sprayed area were made points 
for estimating the fauna populations and noting of changes following the 
sprayings. Two areas on the Iowa side of the Mississippi River, which 
were not treated with DDT, were used as check areas. Ten ponds were 
examined in August and October for fish life with the aid of a minnow 
sweep net and relative changes in populations were noted. While ento- 
mologists from the U. S. Public Health Service, Mr. Clarke and Dr. Searls 
were present, no attempt was made to check closely on insect populations. 
EFFECT OF DDT ON ANIMAL LIFE 
Insects 
Within 30 minutes after the oil spray fell, insects began to shower 
down through the forest canopy. In general, coverage was effective and 
while entomologists were assigned to note effects on insects, data was 
correlated to explain the presence or absence of bird life. Immediate 
