It’s dusk, arguably the most beautiful part of the day, when the sun has set, the air cools, and the sky turns a deep lavender hue, heralding the appearance of stars and romance. You are outside sipping your wine and inhaling the evening fragrance. She is searching for you, lightly caressing your leg with her delicate touch. Tenderly, she inserts her proboscis into your blood vessel…

There are over 2500 species of mosquitoes. They have existed for over 30 million years. This discussion will focus on Culex pipiens, the common house mosquito, the predominant mosquito encountered in the Bay area. Mosquitoes eat rotting fruit and nectar from flowers (they do not function as pollinators). The female mosquito requires a blood meal to produce eggs. They do not require blood to survive. Male mosquitoes do not bite as a rule (although there is a rare exception, the gynandromorph). Female mosquitoes have only1 sexual encounter during their life span of 2-4 weeks. They have the ability to store sperm and dispense sperm internally to fertilize eggs on an as needed basis.

Why are they attracted to you?
Mosquitoes are attracted to humans by our carbon dioxide and lactic acid production that is contained in our sweat and exhalations. They have special sensors for C02 and lactic acid. When you swat mosquitoes away, the energy expended by waving your arms releases more C02 and lactic acid. Swatting also stimulates the mosquito’s visual receptors and creates changes in the air pressure that also makes it easier to detect you. In mosquito language, you are transmitting the message, “Hey, I’m over here!” The human scent plume is heavier than air and sinks toward the ground; this is why mosquitoes prefer to fly low. Mosquitoes are not attracted by perfume.

Genetics definitely play a role in how attractive you are to mosquitoes. It also determines how your skin reacts to the bite. Some people will develop large red swollen areas of skin that itch intensely and others may not even notice they have been bitten. Cholesterol is produced in the skin and is a chemoattractant for mosquitoes. Certain individuals have a higher concentration and thus are bitten more. Certain types of acids such as uric acid and lactic acid are produced in higher concentration in the skin also attracting mosquitoes. Larger people, pregnant women, and actively exercising bodies produce more C02 and lactic acid. A mosquito can detect you 50 meters away. It takes a mosquito about 90 seconds to complete a full blood meal, she extracts 2-3 x her weight in blood. After completion of her dinner, she struggles to fly away and hunts for the nearest wall or plant. She will spend about half an hour concentrating the blood and urinating out excess fluid as water.

 

The majority of infections is asymptomatic or has nonspecific flu-like symptoms such as headache, fever, malaise, and achy muscles. However, potentially fatal complications such as encephalitis (inflammation of the brain) can occur.

Why Are There Mosquitoes?
Mosquitoes are responsible for more human deaths than any other living organism. Some scientists believe Mother Nature has assigned them the role of controlling human overpopulation of the planet. Mosquitoes also protect jungle habitats from being destroyed by man.

How to Avoid Being Bitten by Mosquitoes; Insect Repellants

Permethrin
Wear clothing that has been treated with permethrin. You can purchase clothing that has been treated or you can spray your clothes yourself with products such as Duranon, Sawyer’s, Permanone, Buzz Off or Insect Shield Clothing. Spray your clothing outside and let it dry for 2-4 hours. The spray lasts for six washings. If the article of clothing is not washed, the permethrin will last 6 weeks before the clothing needs to be retreated. “Bugs Away Clothing” is effective up to 70 washings. Permethrin can be sprayed on mosquito netting and screens for added protection. It is only effective when used as a clothing treatment. Permethrin is a contact insecticide and will kill mosquitos, fleas, and ticks. Permethrin has no insect repellant benefit when applied to skin. Permethrin is poorly absorbed by skin. It is inactivated by an esterase in the skin in about 20 minutes.

DEET
N, N-diethyl-M-tiluamide or DEET is the most effective mosquito repellant at a concentration of 30%. The product 3M Ultrathon was produced for the U.S. Military. It contains 33% DEET in a polymer and is long acting. The polymer blocks skin absorption of DEET and decreases the loss of DEET from the skin surface by evaporation. DEET repels ticks, biting gnats, chiggers, fleas, flies, and mosquitoes; it does not kill them. DEET works by evaporation. Mosquitos intensely dislike the odor of DEET (and so will you) although they can still detect your C02 production. The American Academy of Pediatrics states that low concentrations of DEET (10% or less) are safe to use on infants over 2 months old.

Read the directions on the back of the bottle before applying DEET. It is a powerful solvent and will destroy plastics (glass frames, wrist watch, etc.), and synthetic fabrics such as rayon, nylon, spandex. Cotton and wool fabrics are fine. DEET can be a skin irritant and cause a red rash. Overuse can cause neurologic problems.
Applying DEET and sunscreen concomitantly will make sunscreen protection less effective.

Picaridin
Picaridin is another insect repellant that has been available since 1998. It is as effective as DEET but is odorless and has a lighter feel when applied. It is safe for children older than 2 months according to the CDC. It is the active ingredient in Cutter Advanced.

IR3535
Avon's Skin-So-Soft, has been marketed as a mosquito repellent it is much less effective than DEET. The active ingredient is IR3535.

Metofluthrin
Metofluthrin was approved by the EPA in 2006 as a mosquito repellent. It is marketed as DeckMate Mosquito Repellent. It is sold as a paper strip that you place in outdoor areas like patios and decks. It also comes in a container that is meant to be worn a belt. A battery-powered fan releases metofluthrin into the air, surrounding and protecting the wearer. It is not applied to the skin. You can purchase replacement cartridges of metofluthrin.

Encourage Mosquito Predators into Your Garden

Be nice to bats, praying mantis, crane flies, dragonflies, toads, frogs, salamanders, birds, spiders, Gambusia (mosquito fish), and geckos. They eat mosquitoes.

Be Hairy. You have a better chance of feeling the mosquito land on you. Your hairs will activate pressure receptors in the skin when the mosquito lands on you.

Non-Chemical Insect Repellants

These are not as effective as chemical repellants. Citronella, cedar, peppermint, pennyroyal,canola, cajeput, lemongrass, and geranium oils and candles provide temporary, short lived protection, at best 30 minutes. There is a soy-based repellant called Bite Blocker that provides about 1.5 hrs of protection from bites. Oil of lemon eucalyptus appears to offer protection similar to low concentrations of DEET and is safe for children older than 3 years. It is available as a spray on product called Repel. Neem oil applied to the skin is another option. It has insecticidal compounds calle dazadirachtins. Plant rosemary, lavender and marigolds in the garden or keep them on pots around and on your outdoor dining areas. Remove containers and puddles of water that serve as a breeding ground for mosquito larvae. This includes bird baths and tires.(Yikes, the tire swing!) Current research is focusing on thyme, fennel, clove, and celery oils as alternative natural insect repellants. It is not recommended you try concocting a home preparation as these undiluted these oils cause a burning sensation on skin. There are no good studies showing that bug patches containing vitamin B1 or thiamine are effective as insect repellants. The best strategy is to wear permethrin treated clothing and use DEET or pircaridin on the skin.