Dear Martha: What can I do to keep the chrome fixtures in my bathroom spot-free?

A: Unsightly water marks are usually caused by mineral buildup from hard water. Avoid using ammonia-based or abrasive cleansers; these may scratch or otherwise damage the fixture's surface. Instead, rub the spots with a soft cloth dipped in white vinegar, and then rinse and buff dry.

To treat stubborn deposits, soak a cloth or paper towel in white vinegar, wrap it around the fixture, and let it sit for about an hour. Afterward, you should be able to remove the spots with little trouble. In the future, keep a soft towel, such as a microfiber cloth, on hand to dry excess water after each use.

Dear Martha: How can I keep mosquitoes and other biting insects under control?

A: One way to reduce the local population is to eliminate pools of standing water, which mosquitoes, gnats and other bugs claim as their breeding ground. Clean out gutters and awnings in which leaves and rain may have collected, drain the saucers beneath potted plants and empty birdbaths, pets' water dishes, and fountains regularly.

Many repellents are available, chemical and otherwise. The Centers for Disease Control and Prevention asserts that the most effective formulas contain the pesticide DEET or Picaridin.Applied as directed, DEET poses little risk to humans or to the environment, according to the Environmental Protection Agency. However, parents should exercise caution: DEET shouldn't be used on infants less than 2 months old or applied to the hands of young children.

Note, too, that DEET can be toxic if ingested, may damage plastics and synthetic materials, and is known to be slightly toxic to birds and freshwater fish. Picaridin, introduced to the United States in recent years as an alternative to DEET, does not present a health or an ecological concern, according to the EPA.

For those who prefer to avoid pesticides altogether, a number of essential oils, such as lemon eucalyptus, citronella, cedar and lavender, have been found to offer a natural, if somewhat weaker, defense against mosquitoes. Various oil blends can be purchased at most health-food stores. Geraniol, an ingredient extracted from geranium oil, has also been lauded for its repellent properties and is an ingredient in sprays and creams as well as in wristbands and towelettes.

Another option is simply to light candles. Mosquitoes are attracted to body heat and carbon dioxide, which is exhaled and released through the skin. Candles can act as a decoy source of both, and those formulated with geraniol or citronella are most effective, according to recent studies. Ultimately, your best defense is to stay indoors at dawn and dusk, when these insects are out in full force.

Dear Martha: How can I keep ants and other insects out of my hummingbird feeder?

A: Filled with sugary, nectarlike water, hummingbird feeders can bring the tiny, jewel-like birds into your yard if you don't have a garden full of flowers. Unfortunately, ants, bees and wasps, especially yellow jackets, also enjoy the sweet syrup, and these insects can contaminate the liquid and intimidate the birds, preventing them from feeding.

Ants are probably the easiest to deter. Some feeders feature an ant moat, which, when filled with water, prevents the insects from reaching the feeding portals. If your feeder doesn't have a moat or you want added protection, spread a layer of petroleum jelly on the hanging wire. The sticky substance forms a barrier that the ants cannot cross. This jelly won't last forever, though, so you will need to reapply it whenever ants reappear.

Bees and wasps are more persistent interlopers, but you can sometimes confuse them by moving the feeder to different locations whenever necessary. Just as hummingbirds are drawn to the color red, these insects are attracted to yellow, so installing yellow traps a few feet away may also minimize their presence. None of these solutions will harm the hummingbirds. *

Questions should be addressed to Ask Martha, care of Letters Department, Martha Stewart Living, 11 W. 42nd St., New York, NY 10036. Questions may also be sent by e-mail to: mslletters@marthastewart.com. Please include your name, address and daytime telephone number.