For four days, Oxitec technicians care for the eggs, watching for those that hatch into wriggling brown larvae. Those "injection survivors," as the company calls them, face a battery of tests to ensure theirgenetic modification is successful.

Soon, millions of these engineered mosquitoes could be set loose in California in an experiment recently approved by the federal government.

Oxitec, a private company, says its genetically modified bugs could help save half the world's population from the invasive Aedes aegypti mosquito, which can spread diseases such as yellow fever, chikungunya and dengue to humans. Female offspring produced by these modified insects will die, according to Oxitec's plan, causing the population to collapse.

"Precise. Environmentally sustainable. Non-toxic," the company says on its website of its product trademarked as the "Friendly" mosquito.

Scientists independent from the company and critical of the proposal say not so fast. They say unleashing the experimental creatures into nature has risks that haven't yet been fully studied, including possible harm to other species or unexpectedly making the local mosquito population harder to control.