Transparency copy of a print advertisement for Dursban, an insecticide marketed and sold by the Dow Chemical Company for use against mosquitoes. The advertisement features an illustration of several snowy egrets in a marshland environment. The accompanying text details efforts to test Dursban's effectiveness against the Salt Marsh Mosquito and its impact on fish, birds, and other animals living in swampland near the Dow facility in Freeport, Texas.