their Relation to Disease. 
17 
described will require special measures for their extermination. 
We will consider them in turn. 
Domestic Species. —The most important and effective con¬ 
trol work is the elimination of breeding places. Any small 
collection of water in old tins, bottles, rain-water puddles, etc., 
should be removed. Vessels used for storing water for household 
purposes should be kept covered, and should be emptied at least 
once a week, being allowed to become thoroughly dry before being 
refilled. This precaution is necessary in order to get rid of eggs or 
young larvae which are very liable to cling to the wet surface of the 
vessel. Careful attention must be given to roof-gutters to see that 
no rain-water is allowed to accumulate in sagging ends. Holes in 
trees and similar places in the immediate neighbourhood should 
be filled in. Bain-water barrels and storage tanks should be effec¬ 
tively screened, oiled or stocked with small fish of the kinds which 
are known to prey on mosquito larvae ; or copper sulphate may be 
added to the water in the proportion of one part to 5,000; this will 
not affect the drinking qualities of the water and will kill off all 
larvae. Powdered calomel has also been recommended as a good 
larvicide, but it should only be used in very small quantities owing 
to its poisonous nature. In covered cisterns and wells another 
good larvicide has been found to be flake naphthalene, in the pro¬ 
portion of half a gram to four litres of water. Cesspools are often 
prolific breeding places, and may be dealt with similarly. 
Even when all the above precautions have been taken it is 
probable that some breeding places will remain overlooked or 
inaccessible, and in order to prevent the mosquitoes utilising these 
it is desirable to provide trap breeding places. Earthenware pots 
or bamboo joints placed in shady positions and filled with water 
are effective: they should be emptied out as soon as young larvae 
make their appearance. 
Stream and Pool Species. —Eor these forms drainage is 
the most effective method of control, and in the case of some 
species of Anopheles which live in rapid hill streams, subsoil 
drainage seems to be the only method possible ; it has been 
resorted to with marked success by Watson in the Federated 
Malay States. Considerations of expense and other circumstances 
will, however, often prevent its application on a large scale. 
In open stagnant pools, or slow-moving streams, minnows 
and other small fish and aquatic insects are a valuable aid in 
