Spring is springing here in the midwest and the ants have tunneled out from their winter hibernation. The start of anting season is the perfect time to present a guide to the common urban ants of the region.

This post does not show all the ants from the midwest (you can find a comprehensive list here). Rather, these are the most abundant species active above ground in urban gardens, sidewalks, and homes.

Odorous house ant, Tapinoma sessile

Ants found in midwestern houses are more likely to be Tapinoma sessile than any other species. These are small brown ants with single small waist segment and a distinctive cheesy odor when crushed.


Pavement ant, Tetramorium species

Tetramorium species ("species E" and tsushimae) are common sidewalk ants introduced from Eurasia, and our only common non-native ant. Pavement ants are medium-small, with two waist segments, and hold sprawling battles to establish territorial boundaries, especially in spring.


Acrobat ant, Crematogaster species

Crematogaster is unmistakable for the heart-shaped gaster that can be raised above the body. Acrobat ants (Crematogaster cerasi {pictured}, and C. lineolata) are commonly seen tending aphids for honeydew.


Little black ant, Monomorium minimum

Monomorium minimum is a tiny, slender, shiny ant with a two-segmented waist. These are common ground-foraging ants, but their small size renders them hard to see.


Thread-waisted ant, Aphaenogaster species

Species of Aphaenogaster (especially A. rudis & A. fulva) nest in soil or rotting wood in shaded lawns and parks. They are reddish brown in color with a slender, two-segmented waist, and are generalist scavengers important for the dispersal of the seeds of several native plants.


Thread-waisted parasite ant, Aphaenogaster tennesseensis

Aphaenogaster tennesseensis queens start as parasites invading nests of other thread-waisted ants, eventually replacing the colonies with their own offspring. Worker A. tennesseensis are similar to other Aphaenogaster species but have a broader head and a shiny red gaster.


Acorn ant & crevice ant, Temnothorax species

Temnothorax shaumii (left) and Temnothorax curvispinosus (center) are small ants with a slender, two-segmented waist. An Aphaenogaster thread-waisted ant (at right) shows the relative size. Temnothorax nests in tiny spaces like old acorn husks and crevices in rocks and tree bark.


Thief ant, Solenopsis molesta

One of the smallest midwestern species, Solenopsis molesta is a tiny, elongate, light reddish-brown ant with a two-segmented waist. Thief ants live underground but sometimes enter houses or forage along sidewalks.


Eastern black carpenter ant, Camponotus pennsylvanicus

Camponotus pennsylvanicus is the famous black carpenter ant, perhaps the most damaging pest species in our fauna for its habit of nesting in decaying or water-damaged wood of older houses. Black carpenter ants are large, with a single waist segment, and a light coat of golden hairs on the gaster.


Red-banded carpenter ant, Camponotus chromaiodes

Camponotus chromaiodes is similar to the black carpenter ant, but with red on the back of the thorax, legs, and front of the gaster.


Small carpenter ant, Camponotus nearcticus

Camponotus nearcticus is like a smaller, shinier version of the big carpenter ants. This variable species can be all black or various combinations of red and black.


Chestnut-colored Camponotus, Camponotus castaneus

Camponotus castaneus is among the largest ants in the midwest, light reddish-brown in color with a single waist segment. Unlike other Camponotus, C. castaneus nests in soil rather than wood. This species is commonly seen at night or on cool, cloudy days.


Silky field ant, Formica subsericea

Formica subsericea is a common soil-nesting ant in midwestern lawns. It is medium-large, with a single waist segment, and black with an obvious silvery sheen.


Slender field ant, Formica pallidefulva

Formica pallidefulva is a common soil-nesting ant in urban lawns. This species is somewhat shinier and more slender than the silky field ant, and slightly less hairy than the very similar uncertain field ant. In Illinois, F. pallidefulva tends to be dark, but color varies over the range of the species.


Uncertain field ant, Formica incerta

Formica incerta is a medium-large, single waisted ant. It is slightly hairier than the similar F. pallidefulva and tends to inhabit more natural settings.


Slave-raiding ant, Polyergus species

Each common species of Formica field ant is plagued by a Polyergus parasite (P. montivagus is pictured here) that steals brood during spectacular afternoon raids. The pilfered ants emerge in the Polyergus nest and perform all the foraging, nest construction, and brood care. Slave-raiding ants are recognized by their pointed mandibles and reddish color.


Sidewalk ant, Lasius neoniger

Lasius neoniger is a medium-small reddish-brown ant with a single waist segment and a rather fuzzy vestiture. Sidewalk ants leave conspicuous piles of excavated soil around their nests.


Winter ant, Prenolepis imparis

Prenolepis imparis is easily recognized as a shiny brown ant, medium-small in size, with a large pointed abdomen. They are superficially similar to acrobat ants (Crematogaster), but have a single-segmented waist. Winter ants are most active in cool weather and often disappear during the hottest months.