With over 12,000 species of ants around the world, identifying which ant is pictured can be extremely difficult. Luckily, only a few of these species tend to invade our homes, which is one of the main reasons someone would want to identify an ant. Ants that are the most common home invaders include acrobat, Argentine, bigheaded, carpenter, cornfield, crazy, false honey, field, imported fire, large yellow, little black, odorous, pavement, pharaoh and thief ants.
Look at the color of the ant. Most ants are a shade of brown, but a few ants can also be black, red or yellow. Ants that can be black include pavement, carpenter, acrobat, crazy and little black ants. Ants that can be red or reddish brown include pavement, field, carpenter, pharaoh and large yellow ants. Ants that can be yellow or yellowish include pharaoh, large yellow, thief and acrobat ants.
Estimate the size, if possible. Most household ants are 1/8- to 1/10-inch long. Ants that are smaller (between 1/16 to 1/20 inch) than this include pharaoh, little black, bigheaded and thief ants. Ants that are larger include carpenter ants (3/16 to 1/2 inch) and large yellow ants (3/16 inch). Crazy ants range in size from 1/16 to 1/8 inch, and bigheaded ants range in size from 1/16 to 1/4 inch. Field ants and imported fire ants range in size from 1/8- to 1/4-inch long.
Count the nodes between the thorax and the abdomen on the ant. Ant bodies are divided into the head, thorax and abdomen. The part between the thorax and the abdomen are called nodes. Ants with two nodes include thief, pharaoh, little black, acrobat, pavement, bigheaded and imported fire ants. Ants with only one node include crazy, carpenter, field, false honey, large yellow, odorous house, cornfield and Argentine ants.
Look at the thorax (portion below the head). Field, false honey, large yellow, odorous house and cornfield ants have an uneven thorax when viewed in profile. Bigheaded, pavement and acrobat ants have spines on their thoraxes.
Look at the antennae. The first antennal segment on false honey ants is longer than its head, while on cornfield ants it is not. Pharaoh ants have antennae with 12 segments and an antennal club (end of the antennae) has three segments. Thief and fire ants have antennae with 10 segments and an antennal club with only two segments.
Look for unique features. Bigheaded ants have large, square-shaped heads. Acrobat ants have a heart-shaped abdomen. Crazy ants have long legs and antennas.