In the muddy rivers of tropical America live shoals of aggressive mosquito fish. These predators are only 2 in (50 mm) long, but will attack other fish many times their own size. They also devour huge quantities of aquatic insect larvae, such as mosquitoes. When naturalists discovered the fish's voracious appetite for insects, its frequent breeding and its ability to survive in water temperatures ranging from a few degrees above freezing to almost 38oC (100oF), they saw its potential as a mosquito control.
Introduced into many mosquito infested areas, the fish devoured large quantities of mosquito larvae, greatly reducing the risk to local people of contracting malaria or yellow fever. By these means of control, the fish played their part in the successful completion of the Panama Canal and the settlement of the surrounding lands.