Mosquito Coast

Have you ever wondered why when a group goes camping, some just attract mosquitoes regardless of how much repellent, clothing, citronella candles, or garlic they use!! Have you ever wanted to be the person to invent a foolproof mosquito barrier and really make it rich? In this case study you are going to be allowed to be the inventor of such a product. All you have to do is read the scientific evidence below and put your most scientific and entrepreneurial hat on. You may be the next Bill Gates.

What We Need to Know

Where do mosquitoes breed? What is their life cycle?
What are their feeding habits? Why do mosquitoes feed on animal blood? If mosquitoes feed on people, why are there so many of them in the great North woods of Canada where there are no people to bite?
What is dangerous about the mosquito?

Scientists are quite sure that mosquitoes are attracted to carbon dioxide. That would make sense because animals upon whom they prey give off lots of carbon dioxide during respiration. But what puzzles mosquito researchers is that mosquitoes usually bite on hands, legs, and arms. There would not be that much carbon dioxide given off by the extremities of the body. It has been hypothesized that the skin may give off other attractants besides the gas CO₂.

Researchers can collect hand odor on glass beads and use these beads to extract compounds, then analyze the components that attract the mosquitoes. Chemists who analyze the chemical odors say that there may be over 1000 compounds from the skin that the mosquitoes react to. Lactic acid seems to be one of the most powerful mosquito attractants on the skin. However, it is felt that mosquitoes react to a combination of 346 compounds, and these must be in the correct proportions or the mosquitoes will ignore the smells. Two smells that attract mosquitoes are Limburger cheese and stinky feet!

The most common repellent used commercially is a chemical called DEET or N,N-diethyl-3-methyl-benzamide: however, some people fear that the chemical is harmful to humans. There is a constant focus to find a naturally occurring repellent that will minimize those fears in buyers of commercial products. DEET is a chemical that is aerosolized on the skin and repels mosquitoes once they land on the skin. However, DEET does not repel all species of mosquitoes.

What We Need to Know

How many different species of mosquitoes are there? Which ones carry diseases?
Why would mosquitoes select some people to bite and not others based on the information given above?
Why would researchers be interested in finding attractants if their mission is to repel or kill the mosquito?
Can you think of any other applications if human smells, like human "fingerprints," could be analyzed?

Assignment

Design an experiment of your own to test what mosquitoes may be attracted to or repelled by. Discuss the apparatus you would use, the controlled trials that you would perform, the hypotheses you are testing, and the methods of conducting the experiments.

Next, design a chemical compound to eliminate or repel mosquitoes from human and animal skin. Name the compound and market it!

RESOURCES

Wu, Corinna. 2000. Mosquito magnets: Your skin chemicals lure blood-sucking insects to their next meal. Science News. April 22.

http://www.colostate.edu/Depts/Entomology/courses/en570/papers_2000/pike.html

http://www.ars.usda.gov/is/AR/archive/feb00/mosq0200.htm