Family: Formicidae

There are many types of ants that may be found in houses. Some are actual household pests, while others occasionally wander in to look for food or water.

The most common species found in houses in the Northeast include: carpenter ants (Camponotus spp.), pavement ant, (Tetramorium caespitum), and odorous house ant (Tapinoma sessile). Additional species

frequently found indoors include: cornfield ants (Lasius spp.), yellow ants (Acanthomyops spp.), acrobat ants (Crematogaster spp.), thief ants (Solenopsis spp.), little black ant (Monomorium minimum), and

pharaoh ant (Monomorium pharaonis).  Carpenter ants can cause costly structural damage by their excavation of nesting galleries in wood.


Ants have three body regions (head, trunk, and gaster) distinctly defined by narrow constrictions. They have elbowed antennae, and the gaster is attached to the thorax by a waist that consists of one or two

small separated segments. There are three distinct castes of ants: queen, male, and worker. There may also be different forms of each caste. Ants always live in societies known as colonies. Workers are wingless, but at mating time swarms of males and females are produced, usually winged.


ant-vs-termitePeople often confuse winged termites with ants, which often swarm at the same time of year. To differentiate, look at the midsection, antennae and wings.

  • Midsection: The ants have “wasp waists.” Between the thorax and the abdomen is a narrow connection in ants, just like with wasps. The termites do not have this slender waist.  Their width continues, gradually increasing, from the thorax to the abdomen.
  • Antennae: Termites have straight antennae; on ants the antennae have elbows.
  • Wings: All four of the wings of a termite are about the same length. The two rear wings of a flying ant are shorter than the front wings.



cornfieldCornfield ants (Lasius species) are relatively small ants (less than 1/8 inch) that are usually light to medium-brown colored. They nest outdoors but sometimes will enter buildings to feed on sweet materials.


pavementPavement ants (Tetramorium caespitum) are ants to have first found their way to Colorado only in the past few decades but now are often the most common species that people notice. They characteristically produce small mounds of soil at entrances of their nest, and nests are often located under pavement or rocks. They are small ants (1/10-1/16-inch), dark- brown colored and have fine grooves that line their head. Pavement ants forage a wide variety of foods, usually consistently preferring greasy materials. Feeding habits shift during the season with higher protein materials being sought when young are being reared and sugars more favored at other times.


fieldantField ants (Formica species) are among the most common ants found in yards and gardens and are observed in homes most commonly in spring. They are black or reddish-brown and black ants of medium size (3/16-1/3 inch) and sometimes are mistaken for carpenter ants. They nest outdoors in loose soil and some produce mounds that incorporate twigs, dried leaves and other plant materials. Migrations into homes occur in spring when soils warm enough to cause colonies to resume activity but cool temperatures prevent normal foraging in yards. Field ants feed on a variety of foods but most often are observed visiting sweet honeydew excreted by aphids and or other sweet materials.


carpenterCarpenter ants (Camponotus species) are the largest ants that occur in Colorado (1/4-3/8 inch) and are particularly abundant in forested areas. They may be either black or black with a reddish brown thorax. They are most similar to the field ants but can be distinguished by examining them in side view, with the thorax of the carpenter ants being uniformly rounded without indentation. Carpenter ants nest in wood, almost always establishing colonies in wood almost always are foragers that will return to an outdoor nest in the yard. Rarely they will establish a nest in the building, always at some point of previous water-damage. Carpenter ants mostly feed on a mixture of dead insects and honeydew.


pharaoh-ant-mdPharoah ants (Monomorium pharoaensis) are minute (1/12 inch), light-brown ants that are adapted to nesting in buildings. Nests can spread extensively through a structure as pharoah ants may frequently move nest locations, produce multiple queens, and may split to form “satellite” colonies. Pharoah ants feed on a wide range of foods that include syrups, jellies, grease, cake, and pet foods. They can be serious pests of hospitals, dormitories and apartments.

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