Separating Anopheles mosquito larvae from pupae using a cold-water solution, a worker (foreground) at the Project of the Sterile Males in Nueva San Salvador, El Salvador, carries out his daily duties. The project, a collaborative effort of the U.S. Department of Agriculture, the U.S. Public Health Service, and the government of El Salvador, works to control malaria by reducing the mosquito population through sterilization. Each of the more than 3,000 trays holds 7,000 larvae. Separated larvae are left to continue their development while pupae are further divided by gender. Males are then removed for sterilization.