Tawny Crazy Ants
Crazy ants are another invasive species of ants we have here in the United States. These dark brown to black ants are native to South American where they are a serious pest too there. Tawny crazy ants or Rasberry crazy ants are fairly small ants (2-3 mm in length). Crazy ants are a unique species of ants due to their erratic and unpredictable running movements.
Like the Argentine ant or the Big-headed ant, these ants can have multiple queens within the colony. They also prefer sweet foods like the honeydew from aphids which they gather and protect. Like the fire ant, these ants have a painful and stinging bite to them. The bites are packed with formic acid which causes a stinging sensation. This acid is typically used for protection from competition, especially against fire ant venom.
While they are fairly common in South America, we are lucky they have not yet spread to Wisconsin. A few parts in Texas and states along the Gulf Coast have found populations of these ants. Crazy ants appear to prefer hot, humid locations near the coast.