342 
MALARIA 
Sometimes the fear of harm by the use of 
larvicides has been more troublesome than 
the larvicides themselves, especially in 
countries unaccustomed to the use of insecti¬ 
cides in agriculture. I have sometimes com¬ 
batted this fear by a very simple demon¬ 
stration : Water was set out in a container, 
larvae introduced, and treated with a dose 
of Paris green sufficient to kill all of them. 
A second container was placed beside the 
first and received the same dose of larvicide. 
After treatment I have myself drunk the 
contents of the second container (the first 
if one previously fishes out the larvae). Of 
course, no harm followed. 
As in the case of arsenicals used in agri¬ 
culture, the person spreading the poison 
should take some simple precautions against 
getting too much dust next to his skin or 
into the nostrils. Usually attention to the 
direction of the wind, proper clothing and 
a bath after work will suffice to prevent skin 
lesions. Where kerosene is used as a di¬ 
luent, especially when on moist sand or 
gravel, such danger should be small. 
Effect on Fish 
There is no published evidence that Paris 
green has any deleterious effect on fish or 
other water fauna predaceous on larvae. 
Effect on Rice Plants 
Rao and Sweet (1937) measured care¬ 
fully the effect of dusting certain rice fields 
in India. Their conclusion was that, with 
a one per cent dilution of Paris green in 
wood ashes used in quantities commonly 
employed for larval control, no effects could 
be demonstrated which indicated that Paris 
green decreased the rice and straw yield or 
increased the amount of chaff. There was 
no indication that stopping Paris green 
treatment was necessary during the period 
in which the rice plants were in flower. 
Frequency of Application of Paris 
Green Treatments 
The interval between applications of 
Paris green to a breeding place must vary 
with conditions, especially with the water 
temperature, and that of about a week is 
suited to most conditions. The proper 
interval can usually be determined by a 
few preliminary observations. Barber and 
Olinger (1931) had to dust every 5 days in 
treating A. gambiae (costalis ) in Africa. 
This species in the warm coastal region of 
West Africa will develop from egg to adult 
in about 7 days. 
Paris Green and Culicines 
Culicine larvae are poisoned by Paris 
green when the poison is ingested, but their 
manner of feeding below the surface makes 
the poison less accessible to them. Barber 
(1925) did many experiments to ascertain 
the effect of Paris green on culicines and 
determined that a fairly heavy mortality 
can be attained in shallow water, where the 
larvae feed on the particles of green which 
have sunk to the bottom. Also one may get 
a good killing where thick vegetation occurs 
in the breeding water just below the sur¬ 
face. 
Griffitts (1927) mixed Paris green with 
wet sand in various proportions, in one ex¬ 
periment with one part of Paris green to 
100 parts of sand. He attained in various 
experiments a killing of 95 to 100 per cent 
of the larvae of different species of culi¬ 
cines. The breeding water varied in depth 
from 2 inches to 1 foot. The wet sand 
served as a “sinker” to carry the larvicide 
to the bottom within reach of the bottom¬ 
feeding larvae. 
King and McNeel (1938) attained under 
field conditions a high percentage of killing 
of Aedes taeniorynchus by means of Paris 
green mixed with water and applied with 
a small pressure sprayer. In another natu¬ 
ral breeding place containing much vege¬ 
tation and infested by Psorophora they 
attained a high mortality with Paris green 
diluted in water and spread by means of a 
sprinkling can. The depth of this water 
varied from a few inches to one foot. Their 
important experiment in treating Culex 
quinquefasciatus by means of Paris green 
spread by autogiro will be described in this 
paper under “Distribution by autogiro.” 
They found that calcium arsenite was 
about as effective as Paris green on culi- 
