Biological Controls consist of natural predators of mosquitoes assisting in keeping the population numbers lower. Dragonflies appear to help in reducing numbers, but the extent to which dragonflies are present is limited. Animals such as bats and small birds, like purple Martins, are believed to eat large amounts of mosquitoes, but studies indicate that mosquitoes make up a very small portion of their diets. Mosquitofish, or Gambusia affinis, are small, darkish, guppy-looking fish native to areas from New Jersey to Florida. They have voracious appetites for the larvae of mosquitoes. In certain areas they seem to be quite effective.