their Relation to Disease\ 
19 
(iii) Coal tar, 1 pint; turpentine, 1 pint; soft soap, 1 oz.; 
water to make up to two gallons, which will effectively treat 
300 gallons of water. 
Sylvan Species. —For these species the method of attack 
should consist in filling in hollows in trees, and collecting and 
burning in the late autumn the dead leaves, etc., from all hollows 
in which rain-water is likely to collect in the winter. Alternatively 
to the latter, the water in the hollows may be well oiled or treated 
with larvicide in the early spring. 
Swamp Species. —Oiling and other methods can sometimes 
be used, but the only effectual and permanent cure for these pests 
is drainage ; the initial outlay on this may be heavy, but in some 
cases, as for example the salt marshes of New Jersey, the expense 
has been much more than repaid through the enhanced value of 
the reclaimed land. 
