Anopheles quadrimaculatus is a mosquito that is commonly found in the United States, primarily in the eastern part of the country, from the East Coast to the Texas Panhandle. The highest densities of A. quadrimaculatus are found in the southeastern United States.
Anopheles quadrimaculatus can be found in many different habitats, depending on its developmental stage. Larvae are found in freshwater aquatic environments, including ponds, swamps, bayous, slow-moving canals, and streams. The larvae seem to be more prevalent in aquatic environments that contain vegetation and in areas that are exposed to sunlight. Although they are most commonly found in clean water, they sometimes occur in heavily polluted water. Anopheles quadrimaculatus larvae also can be found in manmade objects that fill with water, such as agricultural ponds and fields, cans, barrels, and old tires.
Anopheles quadrimaculatus adults typically are found near aquatic habitats. During the day, adults primarily occupy sheltered areas such as hollow trees, animal stables, human habitats, and other manmade structures. Anopheles quadrimaculatus adults have been collected at elevations as high as 300 meters. (Boyd, 1949; Carpenter and LaCasse, 1955; Foote and Cook, 1959; Horsfall, 1972)
Anopheles quadrimaculatus is a medium-sized, light-brown mosquito. The tips of the wings lack the copper color seen in many other species; instead, the wings are entirely brown and scaly. Females have a body length of about 5 mm and a wing length also about 5 mm. Females have a long proboscis and labella with small black setae; palpi are the same length as the proboscis. The antennae are filiform, and the abdomen is black with many yellow hairs.
Anopheles quadrimaculatus exhibits sexual dimorphism in terms of its body size and the morphology of its antennae and palpi. Males have a body length of 5.5 mm and a wing length of 4.5 mm. Like most species in the genus Anopheles, the male antennae are more complex than those of the females. Anopheles quadrimaculatus males can be identified by their large, plumose antennae that have long, brown hairs with a yellow luster. In males, the last two joints of the palpi are larger, with many long, brown hairs.
Two characteristics make it fairly easy to distinguish A. quadrimaculatus from other Anopheles species. Anopheles quadrimaculatus has broadly rounded wing scales on the proximal end of the cubitus, and the scales on its wings form four distinct dark spots. (Boyd, 1949; Carpenter and LaCasse, 1955; Dyar, 1928; Headlee, 1945)
Anopheles quadrimaculatus larvae have long, rounded heads with single dorsal hairs that are highly branched. The thorax is rounded, with short branched hairs and hair tufts. Long feathered hairs are present on the first three abdominal segments. The other abdominal segments have shorter hairs that are less branched. Palmate hairs on the second abdominal segment are pigmented.
Larvae in the genus Anopheles can be distinguished from Culex species by the presence or absence of the respiratory siphon located on the posterior end of the body. Anopheles larvae do not have siphons, while Culex larvae have siphons.
Anopheles quadrimaculatus eggs generally are dark in color and pointed at one end. Buoyant structures on either side of the medial part of the eggs allow the eggs to float on the surface of water. (Boyd, 1949; Headlee, 1945; Howard, 1900)
Anopheles quadrimaculatus develops through four stages in its life cycle, namely egg, larva, pupa, and adult. The egg, larval, and pupal stages occur in aquatic environments. The developmental time in each stage can vary dramatically, depending on the temperature in the environment. Eggs typically hatch after 1 to 3 days; however, hatching can take longer (up to 3 weeks) when temperatures are lower.
Anopheles quadrimaculatus has 4 larval instars. The time between the egg to the fourth instar stage is 5 to 15 days, again depending on the environmental temperature.
Metamorphosis from the larval to the adult stage occurs during the pupal stage, which can last 2 to 6 days. The total life cycle from egg to adult takes about 14 to 27 days when the water temperature averages about 23° C. (Carpenter and LaCasse, 1955; Centers for Disease Control and Prevention, 2012; Keener, 1945; Rios and Connelly, 2012)
Anopheles quadrimaculatus is polygynandrous; both males and females have more than one mate during the breeding season. Mating occurs near aquatic environments, especially near ponds with vegetation. Reproductively mature males typically stay in the vegetation and wait for females to emerge as adults after metamorphosis. As a female emerges from a pupa, males locate her; mating occurs in flight for about 10 to 15 seconds. After mating, a female requires a blood meal so she can provide nutrients to her developing eggs. (Boyd, 1949; Carpenter and LaCasse, 1955; Horsfall, 1972; Keener, 1945)
Immediately upon emerging as adults after metamorphosis, Anopheles quadrimaculatus females are sexually mature and able to mate. Mating begins as females emerge, and breeding can continue through November. The first brood of eggs typically is laid in April or May, after blood feeding begins and the proper temperatures for egg development are reached. Eggs are laid on the surface of the water in aquatic environments; the eggs, equipped with buoyant structures, are adapted to float on water. Females oviposit within about 2 to 3 days after eating a blood meal. Laboratory observations have shown that A. quadrimaculatus females can lay 9 to 12 broods of eggs during their lifetime, where each brood consists of about 200 to 265 eggs. Once oviposition occurs, females can breed again immediately. They continue to breed until they die. (Carpenter and LaCasse, 1955; Centers for Disease Control and Prevention, 2012; Horsfall, 1972; Keener, 1945)
After mating, females seek blood meals so they can provide their eggs with required nutrients. After oviposition, Anopheles quadrimaculatus shows no additional parental investment in its young.
The lifespan of Anopheles quadrimaculatus varies widely, depending on its sex and the environmental conditions. The factors that affect lifespan include temperature, humidity, host abundance, and predation. Anopheles quadrimaculatus females typically live much longer than males, averaging about 21 days, compared to about 7 days in males. The maximum lifespan observed in a female was 62 days; the maximum for a male was 22 days. Females that overwinter die immediately following oviposition in the spring. (Horsfall, 1972; Keener, 1945)
An Anopheles quadrimaculatus larva lies just below the water surface with its body positioned horizontally. It breathes using the palmate hairs on its abdomen, because it does not possess the respiratory siphon evident in Culex species. If temperatures drop below 12° C, larvae often sink to the bottom of the aquatic habitat and remain there until temperatures increase.
Pupae are active, but they do not feed. They obtain oxygen above the water surface but move down the water column if disturbed.
Adults are most active during dawn and dusk, which is when they feed. During the day, when not feeding or seeking mates, A. quadrimaculatus rests in areas that are near the habitats of its host species. These areas may include hollow trees, culverts, homes, and other shaded habitats that allow easy access to blood meals and oviposition sites. Adults typically are solitary and often do not interact except to mate.
In warmer geographic regions, females overwinter in homes or barns; in cooler regions, they overwinter in isolated areas such as caves and storm drains. Females mate before they overwinter; thus, they can oviposit once early in the spring, and they die immediately afterward. (Boyd, 1949; Carpenter and LaCasse, 1955; Horsfall, 1972; Rios and Connelly, 2012)
Anopheles quadrimaculatus has a flight range of about 1.6 km, with the majority of adults staying near the breeding site. Some adults have been observed to stay within about 0.25 km or less of their breeding site. When its hosts are limited, A. quadrimaculatus can increase its range to about 4 km. Densities of A. quadrimaculatus typically decline with increasing distance from hatching sites. An adult may stay in the same area for a long time, often returning to the same host to feed. Males typically stay closer to the breeding site, whereas females have been observed to spend less time near the breeding site and instead disperse after ovipositing. (Boyd, 1949; Eyles, et al., 1945; Horsfall, 1972; Le Prince and Griffitts, 1917)
Anopheles quadrimaculatus communicates through distinct, but low-energy, sounds. The sounds they make are so low in energy that, in general, humans cannot hear them. While females produce higher-energy sounds than males, and male sounds are higher in pitch, both sexes seem to use similar sounds to attract mates, alert others to danger, and exhibit aggression. Mosquitoes can produce these sounds while in flight, while at rest by beating their wings, and by rubbing their tarsi against their wings.
As in other mosquito species, A. quadrimaculatus finds hosts by detecting odor attractants using its olfactory receptors. It is attracted by carbon dioxide, ammonia, and other odors. Anopheles quadrimaculatus may be particularly sensitive to carbon dioxide, as it often bites humans on their heads. Its maxillary palps detect carbon dioxide, while its antennae detect host odors. Researchers suspect that each mosquito species uses different specific odors to locate its hosts; however, not enough data have been collected to rigorously test whether this is true.
Anopheles quadrimaculatus larvae feed on organic material (e.g., plant and animal matter) that is suspended on the surface of the water in which the larvae float. Larvae feed on many different aquatic organisms and seem to exhibit no feeding preferences. In general, A. quadrimaculatus larvae filter feed on small food items; however, if food particles are too large, larvae may macerate and then consume them. Larvae typically macerate filamentous algae by running the food across their mandibles; they consume the particles that break off. The maximum food particle size increases with each larval instar and ranges from 37 to 131 microns. In their natural habitat, larvae typically feed on detritus, plankton, and filamentous algae. Larvae can be raised in the laboratory when fed yeast, algae, broken hay, or ground dog biscuits.
The feeding patterns of A. quadrimaculatus adults differ according to their sex. To produce eggs, females must feed on blood. Female mouthparts are adapted for solenophagy, i.e., feeding directly from blood vessels. Anopheles quadrimaculatus uses a powerful anticoagulant, effective at 1:10,000 or greater dilutions, to assist in feeding. This anticoagulant is introduced into the blood of the host before the mosquito begins to feed; the anticoagulant prevents the blood from solidifying in the mosquito. Females feed on many animals, including humans, cows, horses, pigs, sheep, dogs, cats, and birds. Scientific observations have revealed mixed results regarding the preferred host of A. quadrimaculatus females; host choice appears to depend on the habitat of the mosquito.
Anopheles quadrimaculatus males and females feed on the sugars and nectar of many different plant species. Laboratory experiments indicate that males and females can be maintained with glucose, honey, or other sugary syrups.
Feeding times can vary depending on the host species and the environmental conditions. Adults typically feed from dusk until sunrise; however, they will feed during the day if hosts are readily available. (Boyd, 1949; Horsfall, 1972; Keener, 1945; Metcalf, 1945; Rios and Connelly, 2012)
Mosquito larvae and pupae are eaten by carnivorous insects, fish, and aquatic fowl. When water levels decrease and larvae and pupae become stranded on land, the mosquitoes are eaten by insects such as ants and shore bugs. (Horsfall, 1972)
Adult Anopheles quadrimaculatus females are temporary ectoparasites of many vertebrates, including humans, cows, horses, pigs, sheep, dogs, cats, and birds. The females act as a vector for various diseases. Anopheles quadrimaculatus is the primary vector of malaria in the United States, as it is a competent vector of Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae. These mosquitoes can transmit other important human and livestock diseases, such as West Nile virus, Cache Valley virus, and St. Louis encephalitis virus. Anopheles quadrimaculatus is a common vector of heartworm (Dirofilaria immitis). It transmits at least three Plasmodium species to birds, although the rate of infection has not been determined.
Given the available information about predation on other mosquito species, A. quadrimaculatus probably is a common source of food for other animals. Many species of birds and bats likely feed on A. quadrimaculatus adults, while many aquatic insects, fish, ducks, ants, and shore bugs likely feed on A. quadrimaculatus larvae and pupae. (Carpenter and LaCasse, 1955; Centers for Disease Control and Prevention, 2012; Hoffmann, et al., 2013; Horsfall, 1972; Keener, 1945)
There are no known positive effects of Anopheles quadrimaculatus on humans.
The largest and most studied negative effect of Anopheles quadrimaculatus on humans is its role as the primary vector of malaria in the United States. Anopheles quadrimaculatus is the primary vector of the most pathogenic agent of malaria, Plasmodium falciparum, along with the less pathogenic strains, Plasmodium vivax and Plasmodium malariae. Malaria has not been a major problem in the United States since the 1940s. Since 1957, 63 outbreaks have occurred in the United States, causing 156 cases that resulted from mosquito transmission. About 1,500 cases of malaria are reported in the United States each year. Due to increased global travel and the common occurrence of A. quadrimaculatus in the United States, the potential exists for more widespread and severe outbreaks of malaria in the U.S.
The Centers for Disease Control and Prevention, along with state and local health departments, carefully monitor cases of malaria and have enacted control measures to combat the infectious disease. ("Locally Acquired Mosquito-Transmitted Malaria: A Guide for Investigations in the United States", 2006; Boyd, 1949; Centers for Disease Control and Prevention, 2012; Headlee, 1945; Rios and Connelly, 2012)
Anopheles quadrimaculatus is a vector for other diseases, including Cache Valley virus. The disease rarely is diagnosed in humans; infections primarily afflict sheep, along with other livestock, such as cows, horses, and small ruminants. Whether this mosquito is the primary vector for Cache Valley virus in the U.S. remains unknown.
The mosquito also carries West Nile virus, which can cause death in humans and other animals, including dogs, cats, horses, and birds. In 2009, 663 cases of West Nile virus were reported in the United States, with 30 cases resulting in death.
Anopheles quadrimaculatus also is a common vector of Dirofilaria immitis, which is the agent that causes heartworm in dogs and cats. This disease can seriously harm household pets, and a great deal of money is spent on its prevention and treatment.
Because A. quadrimaculatus and other mosquito species are vectors for several serious diseases, methods of reducing their populations have been implemented, such as minimizing breeding habitats (stagnant water) and applying insecticides. (Campbell, et al., 2006; Centers for Disease Control and Prevention, 2013; Hoffmann, et al., 2013; Horsfall, 1972; Nayar and Connelly, 2011; Rios and Connelly, 2012)
Anopheles quadrimaculatus is common throughout its wide geographic range, and its population size is not likely to decline in the near future. Any efforts to control A. quadrimaculatus populations focus solely on reducing their numbers, because the mosquitoes are disease vectors.
Paul Glyshaw (author), University of Michigan-Ann Arbor, Elizabeth Wason (author, editor), Animal Diversity Web Staff, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
either directly causes, or indirectly transmits, a disease to a domestic animal
uses smells or other chemicals to communicate
active at dawn and dusk
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
mainly lives in water that is not salty.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
an animal that mainly eats blood
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
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