336 
MALARIA 
water and 0.5 per cent sodium lauryl sul¬ 
fate. This concentrated stock emulsion is 
mixed with about 10 parts of water before 
spraying. While the diluted spray con¬ 
tains only about 6 per cent oil the small 
quantity of pyrethrins greatly increases its 
toxic properties (Ginsburg 1937a), so that 
it is equally as efficient as straight mosquito 
oil in destroying larvae and pupae, but is 
at the same time non-injurious to fish, 
waterfowl and plants. This preparation 
was found useful wherever oil is objection¬ 
able and where a long lasting film is of no 
importance. It was also found valuable in 
protecting outdoor gatherings from mos¬ 
quito annoyance (Ginsburg 1936; 1937b), 
and has been extensively used for this pur¬ 
pose in New Jersey, New York and other 
States. 
Indoor Spraying 
Petroleum oil is also a valuable product 
to exterminate adult mosquitoes in human 
dwellings, barns, stables, trains and air¬ 
planes. An odorless, light petroleum dis¬ 
tillate, containing small quantities of 
pyrethrins (about 0.1 per cent) proved use¬ 
ful not only in killing mosquitoes already 
indoors, but also in repelling those outside 
from entering living quarters through open 
doors, imperfect screens, etc. 
Summary 
Petroleum oils, due to their surface 
spreading and toxic properties, may be uni¬ 
versally employed in mosquito extermina¬ 
tion operations where permanent methods 
of control are uneconomical. In the process 
of breathing on the water surface, the larva 
will inevitably draw in oil from the surface 
film into its tracheal system. Oils of low 
boiling range and high volatility exert a 
direct toxic action and cause death within 
a very short time; high boiling, non-vola¬ 
tile, viscous oils will slowly fill the tracheal 
stems and cause death by suffocation. The 
rate of penetration appears to be propor¬ 
tional directly to the thickness of film and 
inversely to the viscosity of the oil. 
The following are the most essential 
characteristics of an efficient mosquito oil: 
(1) High toxicity to larvae and pupae; (2) 
quick, uniform spreading on water sur¬ 
faces; (3) rapid penetration into the tra¬ 
cheal system; (4) stable, long lasting film 
on the surface. 
On waters where application of concen¬ 
trated petroleum oil is objectionable, the 
New Jersey pyrethrum mosquito larvicide 
offers an efficient substitute, being non-in- 
jurious to man and aquatic life. It has also 
proved efficient in protecting outdoor meet¬ 
ings from mosquito annoyance. 
