Many Michigan residents wonder if fire ants have invaded the state. While these aggressive insects are known for painful stings and rapid spread in warmer climates, their presence in Michigan is generally not widespread or established. Understanding their status and how to differentiate them from native species is important for accurate identification and action.
Current Status in Michigan
Imported red fire ants (Solenopsis invicta) and black imported fire ants (Solenopsis richteri) are not widely established in Michigan. Michigan’s cold winters are unsuitable for their survival and colony growth. Fire ants thrive in warmer, subtropical regions and struggle with prolonged freezing temperatures.
Despite the unfavorable climate, transient individual ants or small, isolated colonies might occasionally arrive in Michigan. This usually occurs through the transportation of infested goods like nursery stock or sod from regions where fire ants are common. Such isolated occurrences rarely lead to the widespread, self-sustaining populations seen in southern states. Michigan remains outside their primary natural range.
Differentiating from Native Ants
Distinguishing imported fire ants from common native Michigan ants is essential. Imported fire ants, particularly the red imported fire ant (Solenopsis invicta), are reddish-brown with a darker abdomen, ranging from 2 to 6 millimeters. They exhibit polymorphism, meaning workers vary in size within the same colony. A key feature is their two-segmented pedicel, a narrow waist between the thorax and abdomen, and antennae with 10 segments ending in a two-segmented club.
Their mounds often lack a central opening. They are known for aggressive stinging behavior if their nest is disturbed, resulting in painful, burning stings that can develop into white pustules.
Native Michigan ants commonly mistaken for fire ants include pavement ants (Tetramorium caespitum) and Allegheny mound ants (Formica exsectoides). Pavement ants are dark brown to black, 3-4 millimeters long, with parallel grooves on their head and thorax. They often build nests under pavement, creating small soil craters at the entrance.
Allegheny mound ants are larger, ranging from 3.2 to 6.3 millimeters, with a reddish head and thorax and a dark brown to black abdomen. They construct large, dome-shaped soil mounds and are known to be aggressive, biting when disturbed. Unlike fire ants, their sting rarely results in the characteristic pustule.
What to Do If You Suspect Fire Ants
If you suspect fire ants in Michigan, take steps for proper reporting and identification. Avoid disturbing the nest or handling the ants directly, as they inflict painful stings. Fire ants are aggressive and will swarm to attack when their nest is disturbed.
Document the suspected ants and their nest. Take clear photographs, including close-ups of individual ants and images of the mound structure. If safe, a sample can be carefully collected for professional identification. Contact the Michigan Department of Agriculture and Rural Development (MDARD) or a university extension office, as they monitor invasive species and pest identification. Prompt reporting aids early detection and helps prevent the spread of non-native species.