The densest population of mosquitoes I've ever met was at Yusufeli in north-east Turkey, where the population fed themselves by irrigated gardens. You needed absolutely impenetrable mosquito nets to sleep. But the other thing that kept you awake at night, until you got used to it, was a continuous roar like an industrial plant or airport runway. It was actually the croaking of thousands of frogs. Guess what the frogs were eating.

Exterminate anything and you take a lot more with it. Ecologically it would make a lot of sense to exterminate Americans, but think how many species of innocent house dust mites and pubic lice depend on them.