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Formerly categorized as T. albipes, this tramp ant species was introduced from the Pacific Island region near Indonesia or Australia, and into Florida sometime before the mid-1980s. It has since become a significant pest in the central and southern parts of the Sunshine State. It also is found in the Hawaiian Island of Oahu, and has spread from Florida into coastal parts of North and South Carolina, Georgia and into Louisiana. In addition, it has been reported in some areas along the western coast of the U.S., and will likely spread further — perhaps aided by the association of colonies with root balls of nursery plants. Antigua, Nevis, Puerto Rico, St. Croix and St. Thomas also report WFA populations.
White-footed ant (WFA) workers are about 0.10 to 0.125 inch long. They are black to dark brown in color, but feature distinct yellowish-white tibia and tarsi on each leg, thus appearing “white-footed.” According to a bulletin from the University of Florida, they look similar to the Argentine ant (Linepithema humile): “However, the petiole of the Argentine ant has a vertical projection that is lacking on the WFA. In south Florida, WFA are frequently confused with Paratrechina bourbonica (Forel), one of the ‘crazy ants.’ Paratrechina bourbonica is slightly larger than the WFA, is faster-moving, has more hair, and emits a slight fruity odor when crushed.”
WFA do not bite, sting or cause structural damage, but is considered to be a nuisance because of its frequent foraging in kitchens and bathrooms, and around the exteriors of homes and buildings.
This ant is primarily a honeydew feder, so it will nest in soil, mulched areas or above-ground locations around landscapes. It tends aphids, scale and mealybugs on plants. However, they are known to also occasionally nest within structures.
WFA colonies frequently become very large, with more than 3 million individuals being common. Research has shown that about half of the colony is comprised of fertile reproductive females, called intercastes, that are inseminated by wingless males.
WFA winged reproductives swarm and leave the colony typically in July or August (at least, in south Florida). After colony formation, the de-alated queen is eventually replaced by the reproductively capable workers (the intercastes). As colonies grow larger, they can occupy many nest sites interconnected by foraging trails, or divide to form new colonies by budding.
The very large colony size, multiple nesting sites and aggressive foraging around and into structures make WFA difficult to control. Research has shown that thorough baiting programs, guided by careful inspections and observations of foraging trails and likely nesting areas, will allow effective suppression.
Although WFA tend to respond best to sweet liquid baits, these baits must be replenished regularly to remain attractive to foragers. Control of honeydew-producing pests on landscape plants can also aid in suppression. Keep in mind that these ants feed on dead insects, so they may also respond to protein-based baits. The use of residual insecticides can be effective; if the ants are foraging or nesting in wall voids or attics, residual dusts may be necessary.
REFERENCES
- University of Florida Bulletin EENY-273, accessed 2/21/23: EDIS.ifas.ufl.edu/publication/IN551
- Truman’s Scientific Guide to Pest Management Operations, Seventh Edition, available for purchase at MyPMP.net/shop
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