Tawny crazy ants spread to 7 Mississippi counties

STARKVILLE, Miss. -- An invasive ant confirmed only in south Mississippi until this year has made moves into nearby counties, causing officials to urge people to be on the lookout for tawny crazy ants.

Joe MacGown, ant taxonomist with the Mississippi Entomological Museum housed at Mississippi State University, said these small, reddish-brown ants are native to South America and first arrived in the U.S. almost 100 years ago.

“According to Mississippi Entomological Museum records, the earliest known record from the U.S. was from Illinois in 1931, followed by records from Florida and Texas in the late 1930s,” said MacGown, who is also a researcher with the Mississippi Agricultural and Forestry Experiment Station. “As with many invasive ant species, they went largely unnoticed until populations exploded in both Florida and Texas in the early 2000s.”

In 2009, tawny crazy ants were identified in Mississippi in Hancock County, and they quickly spread to Harrison, Jackson and Pearl River counties. During this same time period, they were reported in large numbers in coastal Alabama, Georgia and Florida.

“However, over the last 15 years, the spread of the tawny crazy ants seemed to have inexplicably halted until 2026,” MacGown said.

Santos Portugal, entomologist with the Mississippi State University Extension Service, said the ants were identified this year in Wilkinson, Marion and Perry counties.

“If you look at them closely, they are very hairy and have long antennae and long legs,” Portugal said. “They are called crazy ants for a reason, as they appear to run around like crazy more so than form defined trails like you see with a lot of ants.

“But without looking at them under a microscope, one of the biggest giveaways is the sheer number of them, often covering large areas and numbering in the hundreds of thousands or even millions. Once established in these massive numbers, the term ‘super colony’ can be used to talk about them,” he said.

Tawny crazy ants are known by different names, which can confuse people trying to find information about them, Portugal said. In Florida, they were called hairy crazy ants, and they are sometimes called Rasberry crazy ants, named for the pest management professional in Texas who found extremely high numbers of them in the 2000s. 

Various researchers including MacGown compared specimens from different locations and determined that the ants were all the same species, Nylanderia fulva, and the approved common name of tawny crazy ant was given to the species.

“They don’t have large mounds like fire ants, and they tend to nest under things like rocks, fallen limbs, leaf litter or firewood,” Portugal said. “When the populations outside are high enough, they often spill indoors, where their presence becomes a significant nuisance.”

These are significant pests, but the good news is that they don’t sting and their bite is minimal. They tend not to hurt people, although there have been some concerns in the veterinary world because of their sheer numbers.

The ants frequently get into electrical equipment, where they can short out wiring and cause problems. Because of their significant numbers, once they are established in an area, it is unlikely that they will be completely eradicated.

“It is unlikely a homeowner will be able to manage large populations of these ants on their own, so it is important to stay on top of the problem by reaching out to a reputable pest management professional,” Portugal said.

Portugal said the ants had stayed confined to four Mississippi counties for years but spread this year to three more counties. He said pest management professionals in the coastal counties, as well as those in Louisiana and Texas, are reporting a much more active year than normal with these ants. No explanation for this sudden increase in activity has yet been determined.

The public is asked to help in efforts to control the tawny crazy ant by reporting suspicious ants. A physical specimen must be submitted to the MSU Extension Insect Identification Lab for official confirmation.

“Once MSU Extension officially confirms this species in a new Mississippi county, it allows pest management professionals to treat more extensively with a specific product, giving them another tool in their arsenal,” Portugal said.

Because of their numbers, treatment success is not measured by entirely eliminating the pest from the property.

“Success should be measured by the ability to keep them out of the house and other sensitive locations,” he said. “Even with an effective treatment by a pest management professional, follow-up treatment may still be needed. This is often not a once and done thing.”

Visit the MSU Extension Insect Identification Lab at https://extension.msstate.edu/insects/insect-identification to learn more information, including shipping instructions to submit a sample if someone suspects they have found the tawny crazy ant in an area where it is not known to exist.