To fend off aggressive female mosquitoes, L.A. is releasing thousands of sterile males

In Los Angeles, those who wage war on mosquitoes are adding a weapon to their arsenal: more mosquitoes.

The Greater Los Angeles County Vector Control District on Thursday launched a pilot program to release tens of thousands of irradiated, lab-raised mosquitoes into the local environment. These mosquitoes are all male and have been sterilized by the radiation, so the hope is that they will find wild female mates and impregnate them with dead-end sperm, rendering the resulting eggs worthless. 

The target is a particular species, Aedes aegypti. The insects, which...