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Answers to Common Questions About Mosquitoes

RUTGERS COOPERATIVE EXTENSION, NEW JERSEY AGRICULTURAL EXPERIMENT STATION

Why are some people more attractive to mosquitoes than others?

Scientists are still investigating the complexities involved with mosquito host acceptance and rejection. Some people are highly attractive to mosquitoes and others are rarely bothered. Mosquitoes have specific requirements to satisfy, and process many different factors before they feed.

Many of the mosquito's physiological demands are poorly understood and many of the processes they use to evaluate potential blood meal hosts remain a mystery. Female mosquitoes use the CO2 we exhale as their primary cue to our location. A hostseeking mosquito is guided to our skin by following the slipstream of CO2 that exudes from our breath. Once they have landed, they rely on a number of short-range attractants to determine if we are an acceptable blood meal host.

Folic acid is one chemical that appears to be particularly important. Fragrances from hair sprays, perfumes, deodorants, and soap can cover these chemical cues. They can also function to either enhance or repel the hostseeking drive. Dark colors capture heat and make most people more attractive to mosquitoes. Light colors refract heat and are generally less attractive. Detergents, fabric softeners, perfumes, and body odor can counteract the effects of color. In most cases, only the mosquito knows why one person is more attractive than another.

How long do mosquitoes live?

Mosquitoes are relatively fragile insects with an adult life span that lasts about two weeks. The vast majority meets a violent end by serving as food for birds, dragonflies, and spiders; or is killed by the effects of wind, rain, or drought. The mosquito species that only have a single generation each year are longer lived and may persist in small numbers for as long as 23 months if environmental conditions are favorable. Mosquitoes that hibernate in the adult stage live for 6-8 months but spend most of that time in a state of torpor. Some of the mosquito species found in arctic regions enter hibernation twice and take more than a year to complete their life cycle.

Where do mosquitoes go in the winter?

Mosquitoes, like all insects, are cold-blooded creatures. As a result, they are incapable of regulating body heat, and their temperature is essentially the same as their surroundings. Mosquitoes function best at 80ºF, become lethargic at 60ºF, and cannot function below 50ºF. In tropical areas, mosquitoes are active year round. In temperate climates, mosquitoes become inactive with the onset of cool weather and enter hibernation to live through the winter. Some kinds of mosquitoes have winter hardy eggs, and hibernate as embryos in eggs laid by the last generation of females in late summer. The eggs are usually submerged under ice and hatch in spring when water temperatures rise. Other kinds of mosquitoes overwinter as adult females that mate in the fall; enter hibernation in animal burrows, hollow logs, or basements; and pass the winter in a state of torpor. In spring, the females emerge from hibernation, blood feed, and lay the eggs that produce the next generation of adults. A limited number of mosquitoes overwinter in the larval stage, often buried in the mud of freshwater swamps. When temperatures rise in spring, these mosquitoes begin feeding, complete their immature growth, and eventually emerge as adults to continue their kind.

Can mosquitoes carry diseases?

Any insect that feeds on blood has the potential of transmitting disease organisms from human to human. Mosquitoes are highly developed blood sucking insects and are the most formidable transmitters of disease in the animal kingdom. Mosquito borne diseases are caused by human parasites that have a stage in their life cycle that enters the blood stream. The female mosquito picks up the blood stage of the parasite when she imbibes blood to develop her eggs. The parasites generally use the mosquito to complete a portion of their own life cycle and either multiply, change in form inside the mosquito, or do both. After the mosquito lays her eggs, she seeks a second blood meal and transmits the fully developed parasites to the next unwitting host.

Malaria is a parasitic protozoan that infects the blood cells of humans and is transmitted from human to human by Anopheles mosquitoes. Encephalitis is a virus of the central nervous system that is passed from infected birds to humans by mosquitoes that feed on birds as well as people. Yellow fever is a virus infection of monkeys that can either be transmitted from monkey to human or from human to human. Dengue is a subtropical virus that is passed directly from one human to the next. Dog heartworm is a large filarial worm that lives in the heart of dogs but produces a blood stage small enough to develop in a mosquito. The dog heartworm parasite does not develop properly in humans and is not regarded as a human health problem. In some tropical areas of the world, a closely related parasite produces human elephantiasis, a debilitating mosquito borne affliction that results in grossly swollen arms, legs, and genitals.

Can mosquitoes transmit AIDS?

The HIV virus that produces AIDS in humans does not develop in mosquitoes. If HIV infected blood is taken up by a mosquito, the virus is treated like food and digested along with the blood meal. If the mosquito takes a partial blood meal from an HIV positive person and resumes feeding on a non-infected individual, insufficient particles are transferred to initiate a new infection. If a fully engorged mosquito with HIV positive blood is squashed on the skin, there is still insufficient transfer to produce infection. The viral diseases that use insects as agents of transfer produce tremendously high levels of parasites in the blood. The levels of HIV that circulate in human blood are so low that, in most cases, HIV antibody must be used as the indicator to diagnosis infection.