Bacteria to the Rescue
Wolbachia is a naturally-occurring bacteria which is present in over half of all insect species worldwide. The bacteria is already present in many insects in Hawaiʻi, including some mosquito species.
Researchers have found that Wolbachia plays an important role in insect reproduction, because it can function like birth control. Male mosquitoes with one strain of Wolbachia can only reproduce with females with the same strain of Wolbachia. Conversely, males with one strain of Wolbachia cannot produce viable offspring with females with a different strain of Wolbachia, or females without Wolbachia.
In a laboratory setting, researchers can expose mosquitoes to a different strain of Wolbachia and then rear large numbers of them. The mosquitoes are then separated by sex and only male mosquitoes are released into the wild. Male mosquitoes do not feed on blood, only nectar.
Once released, the lab-raised male mosquitoes mate with wild female mosquitoes and those females lay eggs that never hatch. When such releases are completed consecutively, mosquito populations decrease because new generations are not produced in the wild.