PARIS GREEN AND OTHER POISONS AS MOSQUITO LARVICIDES 
343 
cines. King, Bradley and McNeel (1939) 
warn against substituting calcium arsenate 
as a larvicide for tbe more toxic calcium 
arsenite. They (1939) state that “Paris 
green will destroy Culex quinquefasciatus 
in ditches, shallow ground pools, and catch 
basins, although oil is usually preferred, as 
it deters oviposition. ” 
Distribution of Paris Green by 
Airplane 
King and Bradley (1926) have done the 
pioneer work in the use of airplanes in the 
distribution of Paris green for larvicidal 
purposes. They made preliminary tests in 
which dry glass plates and dishes contain¬ 
ing anopheline larvae were placed in an 
open field and treated by airplane. It was 
found that a dosage represented by 10 or 
more granules of Paris green per square 
inch gave a mortality of 100 per cent of 
larvae, that one trip of the airplane at an 
altitude of 15 to 30 feet above the ground 
effectively treated a strip 300 to 400 feet 
wide, and that the quantity of Paris green 
required was at the rate of about one pound 
per 20 acres. These figures would apply in 
natural breeding places only to waters free 
from surface debris, trees and aquatic vege¬ 
tation. 
In their subsequent tests over natural 
breeding places, the authors used a mixture 
of about 10 per cent of Paris green in 
Tripoli earth as a diluent. The amount of 
dust used was regulated by a hopper valve 
within the airplane and varied with the 
amount of brush and trees over the breed¬ 
ing place. In two final tests of 1924, made 
in lakes overgrown with aquatic vegetation, 
the percentage of anopheles killed varied 
from 88 per cent in the first test to 99 per 
cent in the second. Dew caused the dust to 
adhere to vegetation, but when the wind 
was not too strong work could be done after 
the vegetation had dried. It is essential to 
employ skillful pilots who can fly relatively 
low and make proper use of the wind in 
directing the dust cloud. 
The cost of dusting ordinary breeding 
places such as were present in the Louisiana 
area was estimated at fifty cents to one 
dollar per acre, including the cost of the 
larvicide. 
Williams and Cook (1927 and 1928) have 
continued the work of application of Paris 
green by airplane with the cooperation of 
the United States Marine Corps at Quan- 
tico, Virginia. There the production of 
anopheles occurred in flotage consisting of 
mats of eel grass and of water lilies. They 
found that the effective quantity of Paris 
green was one pound per acre, and they 
used principally powdered soapstone as a 
diluent. With wind velocities of less than 
4 miles per hour and flying heights of 100 
feet or less, a 25 per cent content of Paris 
green was effective; while with winds of 
greater velocity and flying heights of over 
100 feet a dilution of 50 per cent was effec¬ 
tive. When breeding was continuous and 
heavy it was necessary to dust at weekly 
intervals. The cost of the material was 
$0,724 per acre. 
Watson, Kiker and Johnson (1938) and 
Kiker, Fairer and Flanary (1938) report 
on the use of the airplane in certain im¬ 
pounded waters. Their experiments were 
done under the auspices of the Tennessee 
Valley Authority. It was found that one- 
half pound of Paris green per acre would 
not afford uniformly effective results, but 
that the distribution of one pound per acre 
gave satisfactory control of anopheline 
breeding except in the presence of dense 
vegetation. Experiments are being con¬ 
tinued by these workers and their results 
will appear in subsequent publications. 
Distribution by Autogiro 
King and McNeel (1938) used an auto¬ 
giro equipped for spraying liquids and 
experimented with Paris green in water on 
the larvae of Culex quinquefasciatus. The 
larvae were contained in dishes arranged in 
two lines, these lines placed at right angles 
to the direction of flight and 500 feet apart. 
The plane was flown at a speed of about 45 
miles per hour and at an altitude of 8 or 
10 feet above the ground. In one experi¬ 
ment, in which 8 pounds of Paris green was 
mixed in 25 gallons of water, the mortality 
of the larvae varied from 61 to 96 per cent 
