The Oxitec method works by introducing a female-specific gene into the insects that interrupts development before females reach a reproductive stage. Populations of healthy males and females can be produced in controlled environments by the addition of a chemical repressor. If the chemical repressor is absent in the genetically engineered flies' diet, only males survive. The surviving males are released, mate with local wild pest females and pass the female specific self-limiting trait onto the progeny resulting in no viable female offspring.