trade name for an organic phosphorus compound that is a general-purpose insecticide considerably less toxic to humans than parathion and is thus suited for the control of household and garden insects. It is important in the control of mosquitoes, flies, and lice. Malathion is a yellow-to-brown liquid with a characteristic unpleasant odour. It is generally prepared by combining O,O′-dimethyl phosphorodithioate with diethyl maleate. It is soluble in most organic solvents except paraffin hydrocarbons, and it is practically insoluble in water. Malathion is readily decomposed by alkalies.