Resistance is the result of gradual, genetic changes in the mosquito population over generations that lead to pesticide tolerance. Resistance development in mosquito populations is practically inevitable if control methods remain unchanged over time. The reason for this is that mosquitoes evolve rapidly. We know that all populations of living organisms change over the course of many generations. Some organisms, like plants, may take one year to produce their next generation as seeds. People may take between 20, or even 30, years to yield the next generation. Mosquitoes can produce their next generation in just two to three weeks. Rapid reproduction of thousands of mosquito offspring in a matter of weeks results in swarms that can evolve around our control efforts. Research has shown that resistance to pesticides can happen in more than one way.
The white paper for mosquito resistance can be found here.