. A civic biology : presented in problems. Biology; Sanitation. THE ECONOMIC IMPORTANCE OF ANIMALS 219 upon the larvae in tho water where the mosquitoes breed will do much to free a neighborhood from this pest. Draining swamps or low land which holds water after a rain is another method of extermination. Some of the mosquito-infested districts around New York City have been almost freed from mosquitoes by draining the salt marshes where they breed. Long shallow trenches are so built as to tap and drain off any standing water in which the eggs might be laid. In this way the mosquito has been al
. A civic biology : presented in problems. Biology; Sanitation. THE ECONOMIC IMPORTANCE OF ANIMALS 219 upon the larvae in tho water where the mosquitoes breed will do much to free a neighborhood from this pest. Draining swamps or low land which holds water after a rain is another method of extermination. Some of the mosquito-infested districts around New York City have been almost freed from mosquitoes by draining the salt marshes where they breed. Long shallow trenches are so built as to tap and drain off any standing water in which the eggs might be laid. In this way the mosquito has been almost exterminated along some parts of our New England coast. Since the beginning of historical times, malaria has been prevalent in regions infested by mos- quitoes. The ancient city of Rome was so greatly troubled by periodic out- breaks of malarial fever that a goddess of fever came to be worshiped in order to lessen the severity \j of what the inhabitants believed to be a divine visitation. At the present time the malaria of Italy is being successfully fought and conquered by the draining of the mosquito-breeding marshes. By a little care- fully directed oiling of water a few boys may make an almost uninhabitable region absolutely safe to live in. Why not try it if there are mosquitoes in your neighborhood ? Yellow Fever and Mosquitoes. - - Another disease carried by mosquitoes is yellow fever. In the year 1878 there were 125,000 cases and 12,000 deaths in the United States, mostly in Alabama, Louisiana, and Mississippi. During the French occupation of the Panama Canal zone the work was at a standstill part of the time because of the ravages of yellow fever. Before the war with Spain thousands of people were ill in Cuba. But to-day this is changed, and yellow fever is under almost complete control, both here and. Swamps are drained and all standing water covered with a film of oil in order to ex- terminate mosquitoes. Why is the oil placed on the surface of the water ?. Plea
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