The common name “little yellow ant” for Plagiolepis alluaudi is no misnomer. At just 2 millimeters long, the diminutive invasive is difficult to detect until it reaches high population density. It was detected in Florida for the first time in early 2017. (Photo credit: University of Florida/IFAS)

“It was just a matter of time before it showed up,” says Thomas Chouvenc, Ph.D.

The little yellow ant (Plagiolepis alluaudi) is a tropical species, native to Madagascar, but it had made its way to the Caribbean sometime in the past decade. And now it’s been found in Florida.

Chouvenc is an assistant professor of urban entomology at the University of Florida’s Fort Lauderdale Research and Education Center (FLREC), part of the UF Institute of Food and Agricultural Sciences. In a report to be published in early 2018 in Florida Entomologist, he and FLREC colleagues Rudolf H. Scheffrahn, Ph.D., and John Warner, Ph.D., document an established population of the little yellow ant in Fort Lauderdale, discovered after a colony had infested a home in the area.

Chouvenc says P. alluaudi shares many traits and behaviors with other “tramp” ant species—invasive, high reproduction rate, supercolonial with many queens, excellent foraging ability—but, at less than 2 millimeters in length, it can easily go undetected until it reaches a high population density.

“What is different from most other tramp species is its size. It is very small, and yet it can outcompete other ant species and form large colonies that bring troubles where it goes,” Chouvenc says. “It has a fantastic ability to spread, because a whole colony can fit in a very small twig, plant debris, or potted plant.”

Unlike some other invasive ant species found in the United States, the little yellow ant does not bite or sting. However, it will likely be difficult to manage. “Baiting can have limited impact on the population, so when it infests a house, recurrent re-infestations are expected over time,” says Chouvenc.

Of the 20 most important pest ant species in Florida, 19 are invasive, which Chouvenc credits to warm weather and human activity. “It is the only place in continental U.S. to have a tropical climate. In addition, it is a hot spot for tourism, has extremely large commercial port activity, and is the capital of the world for luxury yachts,” he says. “With such activity, there is a lot of boat traffic in and out of South Florida to the Caribbean, South America, and other tropical destinations around the world.”

Because the species is of tropical origin, Chouvenc says he is optimistic that it won’t spread far northward. But he and his colleagues will be busy monitoring P. alluaudi in the future. “As we were lucky to catch the invasion early on, we can document and try to understand fundamental processes concerning biological invasions as the species spreads,” he says.