Malaria control is the Navy Medical Department's most important preventive measure in the South Pacific. This corpsman is equipped with a hand spray, the tank of which is filled with No. 2 diesel oil which, when sprayed on stagnant water, is effective up to six days in killing mosquito larvae. Larger stagnant swamp areas are attended to with a power spray mounted on wheels, or are dynamited. After fresh rainfall, these men must promptly cover all mosquito-breeding areas again. Spraying is especially thorough around gun emplacements.