Ants - indoors
Click for larger image Worker ants (Hymenoptera) following the scent trail laid down by the ant that found the food source.

Ants live in colonies either outside or in the house. They are among the most successful and common insects. They can be a nuisance when they go marching across your kitchen counter as they follow scent [pheromone] trails they have laid down to food and water sources.

Symptoms and Diagnosis

First, make sure the insects you have are ants not termites. To distinguish the two, ants have a constricted waist, elbowed antennae, and hind wings that are smaller than the fore wing. Termites do not have a constricted waist, have straight antennae, and both pairs of wings are the same size. Make sure you correctly identify the insect problem before you implement controls.

Life Cycle

What you see in your home are worker ants. These worker ants may live for 4-7 years and collect food to take back to the queen and grub-like larvae in the nest. The queen may live 15 years and is constantly laying eggs to increase the size of the colony. It usually takes 38-45 days from egg to adult. Males will be produced sometime in the life of the colony but they die soon after mating.

Integrated Pest Management Strategies

If the nest is found outside the home

1. Restrict entry points. Trim vegetation away from contact with the house. Also seal as many entry points as possible.

2. Repellants. Plant tansy or mint around the house to deter the ants from entering.

3. Treat the nest. If you can locate the nest, pour boiling water into it.

4. Ant warfare. If more than one nest is located, take a shovel of ants from one nest and put it into the other and let them fight it out.

5. Use an insecticide. Sprinkle diatomaceous earth or granular baits around the perimeter of the house. Read the directions before using any insecticide.

If the nest is indoors

1. Sanitation is key. Do not leave dishes in the sink or food on the counter. Remove ready access to food and moisture. Do not place food items in a trash container until the problem has been solved. Caulk openings where the ants may be entering.

2. Check house plants. If they are in a house plant, remove it, preferably outside, and flood it several times with water or better yet, remove the infested soil and repot in fresh soil. Pitch the plant if that is an option for you.

3. Repellants. Some homeowners report success with repellants. Sprinkle cinnamon, black or cayenne pepper, cloves, bay leaf, mint oil or mint chewing gum unchewed near the trail. Place a white chalk line across the trail may keep the ants from crossing. Spray a mixture of 1 cup white vinegar and 1 cup of water on the countertop.

4. Use baits. These are probably your best option. Your local hardware store will have commercially prepared baits. Solid bait traps work best in late winter and early spring when the workers bring this solid food back to feed the larvae. Adult ants cannot digest solid food. Or you can mix 1 cup warm water with ½ cup sugar and 2 Tbl. boric acid [20 Mule Team Borax]. Put this in bottle caps near their trail. Do not make it too strong. You want the ants to carry this back to the nest to feed to the colony. This may take 3 weeks to be effective. Keep baits away from children and pets.

Ants change their food preferences. They may eat sweet or protein based food at different times. So if one thing does not work, try another.

More images:

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Close-up of a house-invading worker ant (Hymenoptera). Note, elbowed antennae typical of ants.
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A worker ant (Hymenoptera)
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A worker ant (Hymenoptera)
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A worker ant (Hymenoptera)
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Ants (Hymenoptera) collecting honeydew excreted by scale insects (Hemiptera) sucking plant sap from the midrib of an oleander leaves (Nerium)
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Ants (Hymenoptera) collecting honeydew excreted by scale insects (Hemiptera) sucking plant sap from the tender stems of an oleander (Nerium)
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Ants (Hymenoptera) collecting honeydew excreted by scale insects (Hemiptera) sucking plant sap from the midrib of an oleander leaves (Nerium)