
AMERICAN MUSEUM GUIDE LEAFLETS 

spread so well and larve survive between the patches of oil. A 
mixture of about equal parts of kerosene and crude oil is rather 
satisfactory. It should be applied with a spray-pump. Very few, if 
any, of the numerous patented oils are worth the money. “‘Larvicide”’ 
is made from crude carbolic acid; it was used in the Panama Canal 
work, but water treated with it is poisonous to stock. 
Of all the natural enemies of mosquitoes, fish are the most 
important, and of these goldfish are the most dependable and easily 
secured, but small ones are much better than large ones. Top 
minnows, such as species of Gambusia and Heterandria (Fundulus) 
are the most important natural enemies of mosquitoes. It is true 
that numerous aquatic insects feed, to some extent, on mosquito 
larve and pup, but they are rarely numerous enough to be of much 
value, and their numbers cannot easily be increased in any given 
pool. The usefulness of dragon-fly larve and adults has been 
sreatly exaggerated. Tadpoles are vegetarians and do not make a 
practice of eating larve. 
Since Anopheles larve frequently live in water which flows 
rapidly enough to wash away oil, and since they keep close to the 
surface of the water, getting above leaves of aquatic plants where fish . 
do not see them, they are rather difficult to control. To make 
matters worse, they are the mosquitoes which we are particularly 
anxious to get rid of since they are the only ones known to carry 
disease in the North. Cleaning the edges of streams or ponds, 
clearing away aquatic vegetation, and keeping a good stock of fish 
seem to be the only feasible methods of control, although in small 
brooks a constant supply of oil may be furnished from a specially 
designed automatic drip can. 
In regions where malaria or yellow fever or any other mosquito- 
borne disease prevails, such measures should be supplemented by 
careful exclusion of mosquitoes by the use of window screens and bed 
canopies, and special precautions should be taken to prevent the 
biting of those suffering from disease by mosquitoes which may carry 
the infection to others. | 
The application of these various methods of mosquito control, 
with thoroughness and over sufficient areas, has yielded results of the 
most definite and tangible kind. In the Italian Campagna the pro- 
portion of the population infected with malaria was reduced from 
65% to 12% by measures directed toward the eradication of the 
Anopheles mosquito and was then brought down to 4% by the free 
distribution and vigorous advertisement of the value of prophylactic 
doses of quinine. Between 1902 and 1908 the deaths from malaria 
in the whole kingdom of Italy fell from 16,000 to 4,000. 
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