** FILE ** This undated handout file photo provided by the Agriculture Department shows an aedes aegypti mosquito on human skin. Old mosquitoes usually spread disease, so Australian researchers figured out a way to make the pests die younger – naturally, not poisoned. Scientists have been racing to genetically engineer mosquitoes to become resistant to diseases like malaria and dengue fever that plague millions around the world, as an alternative to mass spraying of insecticides. (AP Photo/USDA, File)