Pest Library

Characteristics

There are different species that belong to the genus Formica. The workers’ size will depend on the species, but they are commonly around 4/25 to 3/10 inch in length. They are red, brown, tan, or black. Some species, even have two-colors on them while some larger species are even confused with carpenter ants.

Habitat

These ants, as their name suggests, commonly live in fields. However, they can also be seen in meadows, gardens, parks, and lawns. They build mounds to create a nest. Mounds also differ from species to species. Some mounds can be three to four feet wide and over two feet tall, while others do not rise higher than the height of the grass. Field ants can also create nests under lawns and wood debris that includes firewood piles, bricks and rocks, and more.

Behavior

Field ants are also known by their other names, such as mound ants, wood or forest ants. These ants are not a common indoor pest since they are soil nesters.

These ants do not have a stinger, but they have the ability to bite that may feel like a sting. Some Formica species can even inject plants with their formic acid that can kill plants. When their mounds are disturbed, field ants can bite people and pets.

Food

Field ants prefer the honeydew made by aphids, mealy bugs, and other plant insects. They are considered a beneficial insect because they feed on other insects, such as bed bugs, silverfish, moths, and even termites.

Life Cycle

Most Formica species have multiple queens in one colony, and may create multiple colonies or sub colonies for the main colony. Their colony can survive for ten or more years, depending on the availability of food and the type of species. Queens will lay eggs that will soon become sterile female workers and male drones. Once mating season comes, female and male reproductives will take a nuptial flight that will end for a female reproductive to create a new colony. Other female reproductives can become queens in the old colony. If in the case that the original queen dies, her colony will still survive because of the availability of multiple queens.

Other Information and Tips

Field ants are not known to create nest indoors. However, the large tall mounds that they create outdoors can bring trouble and may make mowing dangerous. Their ability to inject formic acid on plants, especially in woody ornamentals, gardens, and lawns can bring long-term effect on the landscape.

These ants are still beneficial in controlling unwanted insects and should be left alone, especially if their mound is not causing any harm. However, if the mounds are becoming a nuisance and is killing plants, an effective way to control them is to get rid of the mound.

To get rid of the mound:
• Use pesticide labeled for mounds of field ants.
• Exclude the remaining ants from coming into your home by sealing cracks or any other entry points these ants may enter.
• Use insecticide and apply it along the foundation of the home and its perimeter.
• Wait for a couple of days for the mound application to work.

Photo by Richard Bartz, Munich Makro Freak (Own work) [CC BY-SA 2.5], via Wikimedia Commons / resized from original