The common malaria mosquito (Anopheles quadrimaculatus) is actually a group of five species that are genetically different but look so much alike that it is difficult to tell them apart under a microscope. These mosquitoes are present in the eastern United States up into southeastern Canada, but are more prolific in the southeastern states, especially along the Gulf of Mexico. They are the main vector of malaria in North America. Although malaria outbreaks have not happened in the United States since the 1950s, local transmission does occur sometimes.
Common malaria mosquitoes prefer to breed in clean freshwater ponds and lakes with aquatic vegetation. Populations tend to increase after rainfall raises water levels. Their larvae don’t have siphons and, instead, breathe through hairs along the abdomen, so they lie parallel to the water’s surface. Adults are dark with four dark patches on each wing and hold their body angled to the surface when they are resting. Females feed on large mammals at night and rest in dark, cool shelters during the day, which are often inside buildings. These mosquitoes overwinter as inseminated females and can be found indoors during late fall and winter.
Apply a liquid residual insecticide to adult mosquito resting sites in sheltered areas. An insect growth regulator (IGR) labeled for mosquitoes can be applied to standing water in items such as bird baths and planter saucers to prevent larvae from developing into adults. Overwintering females should be knocked down directly to reduce the number that will emerge in the spring.
