Andrew Spielman, Sc.D., is a professor of tropical public health at Harvard University and co-author of the new book Mosquito: A Natural History of Man's Most Persistent and Deadly Foe (Hyperion, June 2001). He answered the questions we've been itching to ask.

Q: Are blondes tastier to mosquitoes than brunettes?
A: Not exactly. For years scientists have been trying to figure out why some people are more susceptible than others, and we still don't know the whole answer. What we do know is that mosquitoes have poor vision, so they respond to contrast-a light coat on a dark background or the reverse. If you're a blonde hiking in the deep woods or a raven-haired person on the beach, watch out.

Q: What else attracts mosquitoes?
A: Movement-swat and you'll keep them around; you'll draw all their little friends too. Since mosquitoes' eyes aren't form-adapted-all they see is light moving across hundreds of sensory lenses-the faster you move, the better they can see you. They're also attracted to moisture and heat, two things you work up when you swat.

Q: Why do mosquitoes go for blood?
A: Actually, only female mosquitoes draw blood-less than three milligrams a day-and only during their reproductive cycle. Male mosquitoes and otherwise-engaged females find that plain old fruit nectar is tasty enough.

Q: What happens when a mosquito bites you?
A: A highly sophisticated sticker comprising a bundle of two tubes and two pairs of cutting stylets plunges a millimeter below the skin's surface in search of a blood vessel. As it strikes, it injects a salivary chemical that inhibits your body's ability to stop any bleeding that might begin.

Q: What causes the itch?
A: When your body's immune system recognizes the foreign salivary chemical, it attacks. This causes a tiny hemorrhage and results in the itchy bump-an allergic reaction akin to hives.

Q: Which parts of the world have the most mosquitoes?
A: The subarctic regions of Siberia, Alaska, and Canada, and also the Everglades.

Q: Do mosquitoes transmit diseases other than malaria and West Nile virus?
A: Yes, dozens, including various strains of encephalitis, Sindbis virus, and O'nyong nyong virus.

Q: Why do mothers always say, "Don't itch"?
A: Because scratching can break the skin and cause a secondary infection.

Q: Does taking your fingernail and putting a little X on the bite stop the itching?
A: I can't imagine what that would do. I find running the bite under hot water-as hot as you can take it-works best. The heat tricks the mind into forgetting about the itching. It's more effective than calamine lotion.

Q: We've heard some mosquitoes are growing resistant to bug repellents. Should we be worried?
A: No. There's some evidence to suggest mosquitoes have grown slightly resistant to the insecticides used in household sprays, such as certain types of pyrethrins, but the repellent deet is still highly effective.

Q: What's tastier-a person's arm or a horse's ass?
A: That depends. There are 2,500 varieties of mosquito. Some are generalists, others specialists. Some attack from above, some from the ground. The malaria-carrying Anopheles gambiae loves the aroma of human feet and plots a ground assault. The common New Jersey mosquito finds the face and neck tastier, and she comes in for an air raid.