• Feed on dead and living insects, aphid and scale honeydew, and juices of ripe fruit; prefer sweets
• Do not feed on wood
• Travel in loose trails
• Forage mostly late in the day or at night
• Prefer moist or humid environments
• Piles of sawdust-like frass and insect parts deposited outside or nearby nests
• Bore into wood to make nests, sometimes causing serious structural damage

• Main colony often outside on tree stumps, dead tree, firewood pile, or fence post
• Consist of extensive networks of galleries usually begun in areas of wood, soft from decay
• May contain several thousand individuals; indoor nests may be satellite colonies of a larger nest outdoors
• Up to 20 satellite colonies can be associated with main colony that contains the queen(s)
• Indoor colonies always associated with moisture and may occur in hollow doors, window or door frames, or the subfloor

When identifying carpenter ants, be sure to look for the smooth, evenly rounded thorax and the 1 petiole node.

• Sweets
• Honeydew
• Insects
• They do not feed on wood

Photo courtesy of UCR Urban Entomology

Carpenter ants deposit sawdust in gallery openings. This sawdust may contain wood fragments, soil, and insect parts. This frass is considerably different from the pelletized frass left by drywood and dampwood termites.

Photo by Laurel Hansen

Carpenter ants nest in wood, hollowing it out as the colony expands. They prefer a moist or humid environment, but will build in dry wood as well. The main part of the colony is usually located outdoors in a dead or dying tree, fence post, or firewood, but satellite colonies, consisting only of worker ants, alates, and pupae may be found inside the home. Some colonies have up to 20 satellites. Queens and brood are always in the main nest. Colonies can have multiple queens.

Once a colony is a few years old and has more than 2000 workers, it will begin to produce new reproductives to start new colonies. Winged males and females are produced in late summer or early spring. Reproductives may also be produced in the late summer and overwinter in the colony to emerge for mating flights in spring. They fly to new locations, where queens hollow out a nest and lay eggs. Infestations are often just recognized during the first warm days of spring when large winged ants emerge from walls or tree stumps.

• Workers are all the same size, 3/16-inch long
• Dark brown to black
• Petiole with 2 nodes
• Thorax uneven with 1 pair of spines
• Grooves on head and thorax
• 12-segmented antennae with 3-segmented club

• Nest in lawns or under stones, wood, or boards
• Mounds are built along sidewalks, baseboards, and near foundations in clusters
• Colonies tend to be found near water
• Usually one functional queen per colony

• Workers are all the same size, 1/16-inch long
• Yellow or honey-colored to orange
• Petiole with two nodes
• Thorax uneven in shape when viewed from side with no spines
• 12-segmented antennae with 3-segmented club

• Feed on both living and dead insects
• Inside, feed on sweets, fats, and proteins
• Travel in set trails along carpets, countertops, cabinets, floors, and baseboards
• Found in places with moisture
• May use electrical wires and plumbing pipes to travel from room to room
• Colonies very mobile; workers, along with larvae, pupae, and even a few queens, may move to new locations if disturbed or if colony becomes too large

• Nest in household structures such as wall and cabinet voids, behind baseboards, behind refrigerator insulation, inside hollow curtain rods, or in the folds of sheets, clothes, or paper
• Outdoors nest in debris or cracks and crevices
• Colonies with up to 300,000 workers with multiple queens

• Workers are all the same size, tiny, 1/32-inch long
• Yellow to light brown with very small eyes
• Petiole with 2 nodes
• Thorax uneven in shape when viewed from the side with no spines
• 10-segmented antennae with a 2-segmented club

• Feed on grease and greasy foods, proteins, dead insects, and even dead rodents; may sometimes feed on sweets
• Often steal food and ant larvae from nests of other ants
• Travel in set trails inside cabinets, on walls, along baseboards, and along branches of trees and shrubs
• May travel from one room to another by traveling on electrical wires; may be seen in electrical outlets.
• Small enough to forage into packaged foods

• Nest outdoors in soil under rocks or in decaying wood
• Indoors, colonies found in cabinet or wall voids or behind baseboards
• Individual colonies small; may have multiple queens

• Workers are polymorphic (different sizes), small, 1/16- to 1/5-inch long
• Body reddish with shiny dark brown gaster with stinger
• Large eyes and 3 teeth on front of head
• Petiole with 2 nodes; no spines on thorax
• 10-segmented antennae with 2-segmented club
• Extremely aggressive

• Feed on living insects, dead animals, and honeydew from honeydew-producing insects
• In homes, forage on sweet foods, proteins, and fats
• Extremely aggressive; if disturbed, will swarm out of nests and attack in large numbers; can inflict a very painful sting
• Travel in distinct trails along foundations, sidewalks, patios, up sides of buildings, along baseboards, and under edges of carpets
• Colonies may split and move to new locations

• Nest in mounds with multiple openings in soil or lawns, usually in open sunny areas near a water source
• If undisturbed, mounds may reach up to 18 inches high and 24 inches wide; they become dome-shaped after 2-3 years
• Nests sometimes found in buildings, wall voids, crawl spaces, or under carpets
• Large colonies of up to 500,000 workers with multiple queens

Red imported fire ants have a long stinger at the tip of the gaster.

• Honeydew
• Sweets
• Protein
• Oil
• Seeds
• Plants
• Insects

In areas that are not disturbed, red imported fire ants typically make dome-shaped mounds that are about 18 inches across and about 8 to 12 inches tall. Red imported fire ants tend to build nests in open, sunlit, grassy areas that are typically irrigated. Because red imported fire ants often build their nests in turfgrass areas in California, frequently the mounds have been mowed and are nearly flat, appearing as soft, loose dirt that obscures the grass and looks like a bald spot in the turf. In some instances red imported fire ants do not build mounds but nest in places such as rotten logs, walls of buildings, or under sidewalks.

After colonies are 1 year old, they begin to produce winged reproductive forms. The reproductives seek out new colony locations during the 6-8 mating flights that occur between spring and fall. These flights usually occur in afternoons after a rainy period when the weather is warm enough. After mating, the fertilized queen sheds her wings and begins building a new colony, and the male dies. Colonies may also propagate by budding where a group of workers leave an existing colony with larvae, pupae, and occasionally queens to establish a new colony. Colonies have multiple queens and may join together to form supercolonies or split into 2 or more colonies. The colonies are very mobile; each one moves at least once every 6 months as a result of extremely wet or dry weather or as a response to an ineffective insecticide treatment. In the hot, dry summer months, colonies may move close to buildings and homes and forage indoors. The peak time for activity is from April through December. There is not much activity January through March.

• Feed on insects, sweet foods, grease, proteins, seeds, almonds, young tree bark, and honeydew
• Active in the morning and early evening and do not trail
• May swarm out of nests if disturbed and can inflict painful stings

• Nest in small mounds or in patches of loose soil near moisture
• Flattened, irregular craters with one to many openings; located usually in warm, sunny areas
• May be found in wood or under rocks and boards
• Indoors, nest in wall voids, crawl spaces, and under carpets
• Colonies very large with up to 10,000 individuals and multiple queens

The southern fire ant has an amber-colored body with a mostly dark abdomen. Golden hairs cover the body.

Note the 2 nodes on the petiole of the southern fire ant.

• Honeydew
• Sweets
• Protein
• Oil
• Seeds
• Plants
• Insects

Southern fire ant nests have fine grained low mounds with one to many openings.

Southern fire ant colonies produce winged swarmers in the spring. Mated flights occur in the spring and may continue through September to establish new colonies. Colonies may also begin by budding where a group of workers leave an existing colony with larvae and pupae to begin a new colony. Occasionally queens will also go. Nest locations change during the seasons of the year as colonies relocate to be near water. Colonies have multiple queens and may join with others to form supercolonies or split to form 2 or more colonies. The peak time for activity is from April through December. There is not much activity from January through March.

• Workers are all the same size, small, 1/8-inch long
• Dark brown to shiny black
• Petiole with 1 node, hidden by abdomen
• Thorax uneven in shape when viewed from side
• Very strong odor when crushed

• Feed on both dead and living insects, favoring aphid and scale honeydew
• In homes, forage primarily for sweets
• Travel in both wandering patterns and set trails
• Trails common along branches of trees, foundations, sidewalks, baseboards, and edges of carpets
• When disturbed, become erratic with their abdomens raised in the air

• Live in shallow nests in soil under stones, wood, or debris
• May nest in various habitats including wooded areas, beaches, wall voids, and around water pipes and heaters
• Large colonies, with up to 10,000 workers and many queens

Odorous house ant trails are common along sidewalks

Colonies begin in the spring and summer months by budding, which occurs when a mated queen crawls out of the nest with some workers to establish a new colony. Occasional late spring swarms, or reproductive flights, may occur. Colonies have multiple queens. Odorous house ants invade homes most likely during rainy weather since their natural food supply (honeydew from insects) is washed from vegetation. Ants can be active all year round in homes, but outdoors they overwinter as workers or larvae until temperatures warm in March, when they begin to forage once more.

When identifying odorous house ants, be sure to look for the uneven thorax, and note the 1 petiole node hidden under the abdomen.

• Workers are all the same size, small, 1/8-inch long
• Uniformly dull brown
• Petiole with 1 erect node
• Thorax uneven in shape when viewed from side
• Musty odor emitted when crushed

• Feed on sweets, fresh fruit, and buds of some plants
• Tend honeydew-producing species
• Forage for sweets and oils in homes
• Travel rapidly in distinctive trails along sidewalks, up sides of buildings, along branches of trees and shrubs, along baseboards, and under edges of carpets
• Colonies may split in spring and summer when queen and workers move to new site; not antagonistic toward each other

• Outdoors in soil, under wood, slabs, debris, mulch, or in branches and cavities of trees and shrubs
• Shallow, 1- to 2-inch deep mounds in open, often disturbed habitats, either moist or dry
• Millions of ants per colony with multiple queens and many subcolonies

When identifying Argentine ants, be sure to look for the uneven thorax and 1 erect petiole node.

• Honeydew
• Sweets
• Ripening fruit
• Insects

New colonies are established in the spring and summer and are propagated by budding, where one or more newly mated queens crawl out of an established colony with a group of workers. Winged reproductive forms are produced in the spring, but there are no flights as observed for other ant species. Argentine ants mate inside the nest. Spring nests are found in open ground. In warmer weather, ants may move nests to more hidden areas such as under houses. The nests in the summer are very shallow, reaching only 1 to 2 inches below the soil surface. There are multiple queens per colony. Queens are very mobile and can quickly move to new locations if conditions are unfavorable. In the fall, colonies merge into larger colonies with hundreds of queens by the process of budding; they remain large throughout the winter. During the winter months, ants may move indoors.

• Workers are all the same size, 3/16-inch long
• Dark brown to black
• Petiole with 2 nodes
• Thorax uneven with 1 pair of spines
• Grooves on head and thorax
• 12-segmented antennae with 3-segmented club

• Nest in lawns or under stones, wood, or boards
• Mounds are built along sidewalks, baseboards, and near foundations in clusters
• Colonies tend to be found near water
• Usually one functional queen per colony