Ants usually nest in soil; nest sites vary with species but are often found next to buildings, along sidewalks, or in close proximity to food sources such as trees or plants that harbor honeydew-producing insects.
They also construct nests under boards, stones, tree stumps or plants, and sometimes under buildings or other protected places.
Ants often enter buildings seeking food and water, warmth and shelter, or a refuge from dry, hot weather or flooded conditions. They may appear suddenly in buildings if other food sources become unavailable or weather conditions change.
In temperate climates the pharaoh ant nests indoors preferring warm, moist locations, often in wall voids, under flooring, or near hot water pipes or heating systems but is also found nesting outdoors in warmer parts.
A new colony is typically established by a single newly mated queen. After weeks or months of confinement underground, she lays her first eggs.
After the eggs hatch, she feeds the white, legless larvae with her own metabolized wing muscles and fat bodies until they pupate.
Several weeks later, the pupae transform into sterile female adult workers, and the first workers dig their way out of the nest to collect food for themselves, for the queen (who continues to lay eggs), and for subsequent broods of larvae.
As numbers increase, new chambers and galleries are added to the nest. After a few years, the colony begins to produce winged male and female ants, which leave the nest to mate and form new colonies.
Common household and structural ants
Argentine Ant – Linepithema humile
Worker is 2.2 to 2.8mm long and has a one-segmented petiole. Antennae are 12-segmented without a club. The body varies in color from light to dark brown.
Odorous House Ant – Tapinoma
Worker is 2.4 to 3.3mm long and has a one-segmented petiole. The body is a uniform brown to dark, and when crused, emit a rotten, coconut-like odor.
Bigheaded Ant – Pheidole
The workers are dimorphic (two size classes), ranging from 1.5 to 4.5mm. They have a two-segmented petiole and a pair of spines on the propodeum. The body color varies from dark brown through shades of red to light yellow.
Pharoah Ant – Monomorium pharaonis
Worker is about 2mm long, monomorphic and has a two-segmented petiole. Body color varies from yellowish or light brown to reddish with the tip of the gaster darkened.
Pavement Ant – Tetramorium caespitum
Worker is 2.5 to 3mm long and monomorphic (one size). It has a two-segmented petiole. Body color varies from light to dark brown to blackish.
Carpenter Ant – Camponotus
Worker is about 5 to 10mm long and polymorphic. It has one-segmented petiole in a form of a vertical scale. The thorax is evenly conves or rounded on the dorsal surface. The body color is dark or red.
Red Imported Fire Ants – Solenopsis invicta
Worker is 1.6 to 5mm long and polymorphic. It has two-segmented petiole and a stinger. The clypeus has three teeth. The body color is an almost uniform dark reddish-brown.