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Mosquitoes: Biology, Repellents & Bite Relief

A mosquito bites a person.
Mosquito bites aren't just a nuisance, they can also carry diseases.
Credit: Mosquito photo via Shutterstock

Nothing ruins a perfect summer evening like the whine of a mosquito in search of a warm meal. There are 176 species of these annoying insects in the United States, according to the American Mosquito Control Association (AMCA) ­— enough to ruin any number of picnics by the pool.

Mosquitoes belong to a family of flies called the Culicidae. Not all species suck blood, but many of those that do can transmit diseases, including malaria. Even disease-free mosquitoes are irritating thanks to their saliva, which causes an allergic reaction in the form of an itchy red bump.

Because of mosquitoes' nasty bites, devices and sprays to repel them are a big business, as is research to improve mosquito repellants. [Related: How to Swat a Mosquito]

The mosquito life cycle

Mosquito control may target biting adults, or it might aim to kill the insect's larvae and eggs. The mosquito life cycle has four stages:

1. Egg. Female mosquitoes lay eggs either on the surface of water or in soil that periodically floods, according to the AMCA. Fish and other predators keep large ponds and streams relatively mosquito-free; instead, mosquito hotspots include temporary puddles, tree holes, old tires and potted plant saucers, according to the U.S. Environmental Protection Agency (EPA).  

Some mosquitoes lay single eggs, while others lay eggs that float together in "rafts" of as many as 200.

2. Larval. Out of the eggs hatch squirmy larvae, which live in the water. Some species hang upside-down from the water surface like stalactites. Others attach to vegetation. Breathing through siphon-like tubes and eating bacteria and algae, the larvae grow and molt four times over.

3. Pupal. After the fourth molt, the mosquito is in the pupa stage. It remains in the water, resting and developing. This takes a couple of days in the common Culex mosquito species in the southern United States, according to the AMCA. In general, the water-living phases of a mosquito's life play out in a few days to a few weeks.

4. Adult. After the adult emerges from the pupal stage, it spends a few days drying its wings and resting. Female adults are to blame for itchy summer bites — males do not feed on blood.

Mosquito repellant and prevention

The first step in keeping mosquitoes at bay is removing the still waters where their eggs and larvae thrive. Get rid of standing water and change water features such as bird baths at least weekly.

The EPA lists several larvae-killing pesticides that are effective at controlling mosquitoes. Insect growth inhibitors such as methoprene prevent larvae from developing into adulthood. Temephos, a chemical that affects the nervous system of insects, can be applied on standing water where mosquitoes breed. Oils applied to puddles can also break up the surface tension that keeps eggs and larvae afloat. Finally, bacteria of the genus Bacillus disrupt the digestive system of insects, ultimately starving them to death.

Mosquito traps often use carbon dioxide or heat to lure the annoying insects in, but scientific studies on their effectiveness are rare, according to the AMCA. DEET and Permetherin-containing insect repellents work on mosquitoes; botanical oils are less effective. A 1996 study in the Journal of the American Mosquito Control Association found that citronella candles and incense did reduce bites under natural conditions, but only by 42 percent and 24 percent, respectively. A 2011 study in the journal of Tropical Medicine & International Health found that citronella candles in indoor tests repelled only 14 percent of mosquitoes. Citronella diffusers (which release more concentrated oil) performed slightly better, repelling 22 percent of female mosquitoes up to 20 feet away.

When skeeters do bite, calamine lotion, hydrocortisone cream and ice are effective remedies against itching and swelling, according to the Mayo Clinic. Oral antihistamines such as Benadryl can also bring relief. 

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Stephanie Pappas

Stephanie interned as a science writer at Stanford University Medical School, and also interned at ScienceNow magazine and The Santa Cruz Sentinel. She has a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science writing from the University of California, Santa Cruz.
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