WINTER NUMBER 43 
used to much better advantage, but none was available for experi- 
ment. As it contains about fifteen times as much nicotine per 
volume as the other decoction, probably no diffieulty will be ex- 
perienced in evaporating a sufficient quantity to kill the mosqui- 
toes if it proves effective. 
Oil of turpentine was tried as a fumigant, but it caught on fire 
so the experiment was discontinued. It burned with a dense 
smoke which completely filled the room, but did not kill the mos- 
quitoes. Green camphor leaves dried in an oven and burned at 
the rate of two ounces per seven hundred feet were not effective. 
It is important that the evaporating vessels for any fumigants 
be placed near the floor, otherwise the mosquitoes near the floor 
will not be harmed, as the fumes are lighter than air. 
PREVENTIVES FOR LARVAE 
Preventive and remedial work against the adults is desirable 
and often very effective, but it is only temporary and does not 
destroy the root of the trouble. It is better, in all cases where it 
is possible, to either kill the larvae or to destroy or render unin- 
habitable the breeding places. It is more satisfactory and usually 
cheaper in the long run to destroy the breeding places. The pecu- 
liar habits and structure of the larvae make it possible to kill 
them rather easily with substances called ‘“‘larvacides.” These 
substances float on the surface, forming a film which prevents the 
larvae from reaching the air with their breathing tubes. Various 
substances have been tried and many have given good results, 
but considering everything, petroleum products have proved the 
most satisfactory. It was suggested as early as 1812 that kero- 
sene was effective in killing larvae, but the use of it did not be- 
come very general until about 1895. Since then it has been used 
extensively with good results. H.W. Weed rid the campus of the 
Mississippi Agricultural College of mosquitoes by oiling eleven 
water tanks. Professor Kellogg found that by pouring a little 
kerosene in some post holes that the mosquito plague was almost 
immediately alleviated at Leland Stanford University. Mr. W. 
C. Kerr did some extensive work on ponds and swamps on Staten 
Island, and Dr. J. B. Smith reports its successful use in two cases 
on Long Island. An oil suitable for this work should be light 
enough to spread rapidly and yet heavy enough not to evaporate 
too readily. A low grade oil known as fuel oil has been found best 
suited for this. Mr. H. J. Quayle (1906) used a mixture of a 
heavy, eighteen degree Baume, oil and a light, thirty-four degree 
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