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Insect Pests

Ants are among the most prevalent pests in households. They are also found in restaurants, hospitals, offices, warehouses, and other buildings where they can find food and water. On outdoor (and sometimes indoor) plants, ants protect and care for honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, increasing damage from these pests. Ants also perform many useful functions in the environment, such as feeding on other pests (e.g., fleas, caterpillars, termites), dead insects, and decomposing tissue from dead animals.


Inside buildings, household ants feed on sugars, syrups, honey, fruit juice, fats, and meat. Long trails of thousands of ants may lead from nests to food sources, causing considerable concern among building occupants. Outdoors they are attracted to honeydew, produced by soft scales, mealybugs, and aphids. This liquid excrement contains sugars, and other nutrients. Frequently outbreaks of scales and aphids occur when ants tend them for honeydew because the ants protect scales and aphids from their natural enemies.

Ants can bite with their pincerlike jaws, although most species rarely do. The velvety tree ant, however, is an aggressive biter. A few ants sting, including native fire ants and harvester ants, which are primarily outdoor species, and are the most common stinging ants in California. An aggressive stinging ant, the red imported fire ant (S. invicta), has recently been found in various southern California counties. If you suspect a fire ant infestation, report it to your county agricultural commissioner. For more information on red imported fire ants.

Monitoring and Inspection

Monitor for ants near attractive food sources or areas of moisture. Ants may invade kitchens, bathrooms, offices, or bedrooms. Inspect under sinks, in cupboards, along pipes, and along electrical wires. Look for large trails of ants or for just a few stragglers. Straggling ants are scouts randomly searching for food or nesting sites. When you spot ant trails, try to follow the ants to where they are entering the building and to the nest if possible. Look for holes or cracks in foundations or walls that provide entry points to buildings.

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