'REMEDIES AND PREVENTIVES AGAINST MOSQUITOES. 15 
minutes. At a larvicide plant at Ancon 4,600 gallons of this mixture 
were made at a cost of $0.1416 per gallon. Although this mixture 
has been used to a large extent in Panama, crude oil was also used for 
streams having a fair velocity. 
THE PRACTICAL USE OF NATURAL ENEMIES OF MOSQUITOES. 
The common goldfish and silverfish destroy mosquito larve and 
should be put in artificial ponds. Top-minnows of several species 
have been introduced successfully in several localities and are great 
feeders upon mosquito larve. Certain species introduced from Texas 
into Hawaii have been successful; and a small top-minnow of the 
genus Girardinus, known in the Barbados as “ millions,” has been 
carried with success to others of the British West India Islands. In 
Rio de Janeiro another top-minnow has been used by the public 
health service for placing in tanks and boxes where it was impossible 
to use petroleum. 
There are many predatory aquatic insects that feed upon mosquito 
larve; others that catch the adults. Certain birds prey upon the 
adults, and they are also eaten by bats. An experiment is being 
carried on near San Antonio, Tex., in which a bat roost has been con- 
structed with the dual purpose of gathering the bats to kill mosquitoes 
of that region and of collecting the bat guano. 
DETERRENT TREES AND PLANTS. 
A great deal has been published concerning the properties of cer- 
tain growing plants which are said to keep away mosquitoes. Among 
these may be mentioned several species of Eucalyptus, the castor-oil 
plant, the Chinaberry tree, and others. Although the evidence in 
regard to these plants is contradictory, all observations made by 
scientific men in different parts of the world negative their value; 
claims that they are valuable are confined to people who have not 
made thoroughly scientific tests. 
[A list showing the titles of all Farmers’ Bulletins available for 
distribution will be sent free upon application to a Member of 
Congress or to the Secretary of Agriculture. | 
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