Search
Madeline Phillips, Carlton, Christopher E.
Anopheles quadrimaculatus, the North American malaria mosquito, is one of the most important mosquitoes in North America when it comes to human health. North American malaria mosquito adults are 5 mm to 6 mm in body length, brown in overall color, with darker brown markings on the abdomens formed by dark scales. The mouthparts of the adult comprise a group of stylets that form an elongate proboscis at the front of the head. The proboscis is straight and rigid in females and curved and flexible in males. The antennae of females are slender, with short hairs on each segment, and plumose (feather-like) in males. Most adult mosquitoes hold their bodies parallel to the surface when at rest, but Anopheles adults hold the body at an angle, with the head down and abdomen up. Dark scales on the wings create a pattern of four dark spots, thus the specific epithet quadrimaculatus. The aquatic larvae (wrigglers) may reach 8 mm in length when fully developed. They rest parallel to the water’s surface, in contrast to other mosquitoes that orient with the head down. Distinctive hair-like processes extend from the tip of the abdomen, but the breathing tube (siphon) present on many mosquito larvae is absent. Eggs are black, oval and are deposited in rafts consisting of six eggs each. Adjacent rafts are connected.
The mosquito genus Anopheles includes at least 70 recognized species worldwide, which can be difficult to identify to species without specialized expertise and equipment. About a dozen species occur in North America. The North American malaria mosquito is a complex of closely related species that can only be distinguished using molecular techniques.
Adult female malaria mosquito in resting position (assmann, iNaturalist, Creative Commons 4.0).
Eggs are laid directly in standing water. The eggs cannot tolerate dehydration, so dry weather reduces survival. Larvae hatch after two to three days in favorable conditions. Larvae remain fully aquatic and undergo four growth stages (instars) before transforming into pupae, which are also aquatic. The pupal stage duration is four to 10 days, during which the active pupae remain near the surface unless disturbed and breath using a set of spiracles that extend through the surface tension. Adult mosquitoes emerge from the pupae and rest briefly on the water surface before flying off in search of a blood meal (females) or a source of nectar or other plant fluids (males). Female mosquitoes require a blood meal for egg development and prefer mammals as prey, in contrast to other mosquitoes that prefer birds or other animals. Adult mosquitoes form mating swarms in the vicinity of larval habitats.
Adult female malaria mosquito museum specimen (rbcl_guy, iNaturalist, Creative Commons 4.0).
As suggested by the common name, this species has been considered historically the main vector (carrier) of Plasmodium, the causal organism of malaria, in the eastern United States, including Louisiana. Malaria does not pose a current threat of epidemic in the U.S., but sporadic cases of locally acquired disease have been reported. Most cases in the U.S. involve persons who have traveled abroad recently to areas where malaria is endemic.
In addition to its status as a potential vector of malaria, the North American malaria mosquito is known or implicated as a vector of causal organisms of numerous other diseases of medical or veterinary importance. These include dog heartworm, eastern equine encephalitis and Cache Valley virus. Modern, research-based public and veterinary health infrastructure and prophylactic treatments have largely prevented the spread of these mosquito-borne diseases during recent years. In addition to the disease vector risks, mosquitoes are serious nuisance pests that suppress outdoor work and recreation in areas such as Louisiana where large mosquito populations occur regularly. Most people experience itchy red bites, but some people may have more severe reactions, depending on susceptibility of allergens in mosquito salivary secretions.
Monitoring and prevention. The best way to prevent bites before they occur is to wear protective clothing. This includes clothing that covers as much of your bare skin as possible, including long-sleeved shirts, pants and tall socks. Close-fitting screens and keeping doors closed are necessary to prevent entry by mosquitoes. When sleeping outdoors, mosquito netting will prevent most bites but must fit tightly around edges.
Natural control and sampling. Eliminating standing water is the most effective way of preventing population buildup of malaria mosquitoes in residential areas. Water sources such as bird baths should be emptied and refreshed every couple of days to prevent larval development. Pruning shrubbery and other areas with dense foliage around homes and keeping lawns mown short can reduce harborage areas for adult mosquitoes. Mosquito sampling is typically done using carbon dioxide baited traps for adults and temporary water sources to survey for eggs and larvae.
Chemical control. Applying an effective mosquito repellent (typically DEET or picaridin based compounds) to exposed skin and thin clothing when going outdoors is the best way to reduce personal risk of mosquito bites. Floating mosquito dunk formulations of the bacterial insecticide Bacillus thuringiensis israelensis are commonly used for small bodies of water. These specifically target mosquito larvae. When conducting homeowner treatments for pests, always follow legally mandated label instructions. Large infestations of adults and extensive larval habitats require treatment by professionals using chemicals that are labeled for mosquitoes. A number of quick knockdown formulations are used for adult mosquito control. Resmethrin, malathion and permethrin are currently labeled for controlling A. quadrimaculatus populations. Resistance to malathion has been reported during recent years, but it can still be beneficial.
Anopheles mosquito larva, highly magnified (Harry Weinburgh, CDC, public domain).
Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology. Reach the department through the Contact Us webpage.
P4013
9/11/2025
The LSU AgCenter and LSU provide equal opportunities in programs and employment.
