PARIS GREEN AND OTHER POISONS AS MOSQUITO LARVICIDES 
339 
1 to 500 of water. This diluted larvicide is 
spread by means of a liquid sprayer. The 
mixture in water must be kept agitated 
somewhat, a purpose which is usually ac¬ 
complished by the act of carrying and using 
the sprayer. One knows that he is keeping 
the contents of the sprayer well mixed if 
the spray-cloud continuously has a greenish 
tint. 
The egg albumen makes an evener mix¬ 
ture in the sprayer and helps to prevent 
clogging of the nozzle. It is best applied by 
making a solution of about 5 gm of dried 
egg albumen in 150 cc of water and adding 
about 4 per cent of this solution to the Paris 
green-kerosene mixture. Or one may add 
the albumen solution to the water-diluted 
mixture in the sprayer, using, of course, an 
appropriately smaller percentage. 
In the proportions employed in the Paris 
green-kerosene method, the kerosene does 
not act as a larvicide per se but functions 
as a vehicle for the Paris green and as a 
means of keeping it afloat. Eventually the 
kerosene evaporates and leaves the particles 
of Paris green free on the water surface, in 
which condition they are presumably more 
liable to be eaten by larvae than when mixed 
with a dust. The kerosene dilution method 
can be employed in any kind of weather, 
just so it is not raining at the time of appli¬ 
cation. 
In one field experiment, about 100 square 
meters of breeding area, very grassy but 
relatively free from surface debris, was 
treated with 2,400 cc of a Paris green-kero- 
sene-water mixture. The dilution was made 
in the proportion of one part of Paris 
green-kerosene to 500 parts of pond water, 
and the amount used represented 5 gm of 
pure Paris green. Before treatment this 
area contained 1 to 20 larvae ( A. maculi- 
pennis and A. elutus) per dip; while on the 
following day no living larvae could be 
found. 
Barber, Rice and Mandekos (1936) de¬ 
vised a method for spreading the Paris 
green-kerosene mixture without the use of 
the sprayer or egg albumen—a method 
especially useful where an abundance of 
sand or fine gravel is present. The Paris 
green-kerosene mixture is well mixed in 
moist sand or gravel in the proportion of 
about 30 cc to 3 liters of sand or gravel. The 
degree of moisture of the diluent is im¬ 
portant. If too wet, it cannot be easily 
spread. If too dry, the Paris green-kero¬ 
sene will “paint” itself on the dry particles 
and may sink to the bottom with them; 
while particles suitably moist will give up 
their larvieides in the form of a blotch or 
film when they touch the water. A simple 
rule is to make the mixture of sand or gravel 
with the larvicide moist but not too wet to be 
easily strewn. One can often get the right 
moisture by blending wet and dry sand at 
the stream-side. 
The sand or gravel can be easily strewn 
by hand and may be directed to any part of 
the breeding place, even against a strong 
wind. The larvicide thus prepared is less 
liable to get into the clothing or nostrils of 
the operator, for it does not separate from 
the moist vehicle until it reaches the water 
surface. One may add a spreader to the 
Paris green-kerosene mixture in the form 
of oleic acid (one per cent or less) or of some 
vegetable oil or resin. But such spreaders 
do not seem to be necessary for good filming 
except in cooler waters. "Wind, of course, 
aids in the spread of films. One may use 
this form of larvicide immediately after a 
rain, if desired. 
"We made an experiment with Paris green- 
kerosene-gravel in a pool containing many 
anopheline larvae—over 3 per dip. The 
Paris green-kerosene mixture was spread 
over wet pebbles each of which was about 
1.5 cm in diameter. Certain pebbles were 
distributed in water surfaces of known area 
and more or less confined by the bank or 
other natural barrier. From a single pebble 
the larvicide spread about one-half yard in 
one direction and from one and one-half to 
three yards in another, practically “steri¬ 
lizing” this area. The next day we found 
many dead larvae (some of them with Paris 
green still demonstrable in the intestine) 
and only one living one. The water of this 
pool contained little debris and its surface 
had been cleared by a recent rain. 
In a laboratory experiment, a single grain 
