What is the purpose of surface film agents in mosquito control?

• A. Effective in the larval and pupal stage through mineral oil that suffocates insects by blocking their ability to breath through their siphon
• B. Effective only against adults
• C. Creates a habitat for predators
• D. Increases water pH to kill larvae

Answer: (A)

Surface film agents work by forming a thin layer on the water that stops mosquito larvae and pupae from getting air. These insects breathe at the surface through siphons or trumpets that stick out of the water. When a mineral oil film covers the surface, it blocks access to air for those breathing structures, causing suffocation and death in the larval and pupal stages. This method targets immature stages at the water surface, so it doesn’t affect adults, and it doesn’t create habitat for predators or alter the water’s pH. That’s why the description that mineral oil suffocates larvae and pupae by blocking their breathing at the surface is the best match.