386 MOSQUITOES OF NORTH AMERICA 
half an hour, and 1 part to 5000 parts of water will kill anopheles larva in from 
five to ten minutes, or less. This property of killing larve rapidly is of great 
importance in the Tropics, where continuous rainy periods make crude oil or 
kerosene much less valuable as a larvacide than it is in northern latitudes having 
less rainfall. Also the larvacide acts as an algecide, and thus destroys the food 
and the hiding places of anopheles larve. As it takes up very little room, com- 
pared with the area it can be spread over, the cost of distribution will be much 
less than that of crude oil or kerosene—considering the large territory which 
the antimalarial work covers, this item alone is of great financial advantage to 
the department. 
“Tests have recently been made to determine approximately how much of the 
new larvacide will be needed per month (rainy season) for each district. 
“ Although this larvacide will be used to a large extent, yet we shall con- 
tinue to use crude oil for streams having a fair velocity, as such application gives 
excellent results and is as economical as larvacide would be, as the oil is spread 
in a very fine film automatically. In order to make the crude oil drip with con- 
tinuous regularity, a piece of metal similar to that part of a flat-wick lamp 
which holds the flat wick is fastened to the oil container. It is made somewhat 
larger than the wick, so that the wick fits it loosely when saturated with the 
grade of fuel oil we use. This metal wick chamber is fitted to the oil container 
about 3 inches from its base. The space below the wick chamber is filled with 
a solution of caustic soda or of larvacide. As the oil is attracted along the wick 
by capillary attraction, it comes into contact with the larvacide or caustic soda 
and is ‘cut, rendered thinner. This method of procedure prevents the wick 
from being clogged by the thick fuel oil and enables the wick to drip the oil 
desired.” 
In the September, 1909, report, it is stated that the new larvicide was giving 
very satisfactory results and would undoubtedly reduce the cost of anti-malarial 
work, besides being more effective than crude oil in many places. It also has 
some value as a destroyer of vegetation, thus making conditions less favorable 
to mosquito breeding. In the October report satisfaction with its use is again 
expressed, and it is stated that the fact that it kills the grass at the edges of the 
ditches will be of importance in reducing the cost of anti-malarial work. 
Mr. August Busck, of the Bureau of Entomology, U. 8. Department of Agri- 
culture, has recently had an opportunity to witness the effectiveness of this 
preparation and has furnished us the following account of its effects and manner 
of application: 
“ Friday I had a very excellent opportunity to observe the application and 
result in the field, in one of the outlying districts, near Rio Grande on the 
Isthmian Canal Zone. Here was about a mile and a half of a small slow-run- 
ning stream, passing through a scattered native village and through thick brush, 
which for some reason had been overlooked or neglected. This was literally 
swarming with Anopheles larve and pupe everywhere along the grassy edges 
and in the small pools caused by the native washerwomen, or by pigs, poultry 
and horses. It was about as nasty a place as I have seen, producing thousands 
of adults every day. 
“ The local sanitary inspector, Mr. Trask—one of the most efficient—kindly 
postponed action until I had been over the ground thoroughly, and then started 
a man with a knapsack-pump, another with larvicide supply for the pump and a 
foreman to oversee the job, from the head spring down along the stream; they 
walked right along and sprayed with a 1 to 6 solution as they went, covering 
