The Red Imported Fire Ant (RIFA), Solenopsis invicta, is an aggressive, invasive species native to South America, known for its painful, venomous sting and the large mounds it builds. Concerns about its spread have reached northern states. While Pennsylvania’s climate limits widespread establishment, isolated populations have been found, usually arriving in shipments of nursery stock or sod from southern states. This article clarifies the current status of RIFA, provides identification details, and outlines the steps residents should take if they suspect an infestation.
Current Status of Imported Fire Ants in Pennsylvania
The presence of the Red Imported Fire Ant is generally not established across Pennsylvania in the same way it is in the southern United States. The state’s cold winters act as a natural barrier, making widespread, permanent colonization difficult. Isolated colonies of RIFA have been documented in localized areas, typically introduced through the movement of regulated materials like contaminated soil, plants, or hay.
To prevent artificial spread, the federal government has established quarantine zones enforced with the cooperation of state agencies. For Pennsylvania, the quarantine status often targets the southeastern corner of the state, which is the most common point of entry and has the milder climate. The quarantine helps to contain any accidental introductions, ensuring that materials like soil, sod, and nursery stock are not moved from regulated areas without proper inspection.
Identifying Fire Ants Versus Common Native Ants
Accurate identification is important for residents to determine if they have encountered a true fire ant or one of Pennsylvania’s many native species. The Red Imported Fire Ant is a polymorphic species, meaning worker ants within the same colony vary in size, ranging from approximately 1/8 inch to 1/4 inch in length. Their coloration is typically a uniform reddish-brown, often with a darker abdomen.
A specific morphological feature is the two-node, or two-segmented, waist (pedicel) connecting the thorax and the abdomen, which differentiates them from many other local ants. Their nests are also highly distinctive, appearing as loose, dome-shaped mounds of soil that can reach up to 18 inches in diameter. A key identifying trait of a RIFA mound is the absence of a central opening or crater, as the ants exit the nest through underground tunnels.
In contrast, common nuisance ants in Pennsylvania, like Pavement Ants, are much smaller and darker, and their nests have distinct entrance holes. Carpenter Ants are much larger, ranging up to a half-inch, and do not build the characteristic soil mounds. If an ant is disturbed, the RIFA will aggressively swarm and sting repeatedly, resulting in a characteristic white pustule that forms hours later.
Action Steps for Residents: Reporting and Quarantine Compliance
If a resident suspects they have located a Red Imported Fire Ant colony, they should not attempt to treat the nest or disturb the mound. Disturbing the nest can cause the colony to disperse, making official eradication efforts much more difficult. The correct first step is to immediately contact the Pennsylvania Department of Agriculture (PDA) or a local Penn State Extension office.
These state and local authorities can provide guidance on safely collecting a sample, if necessary, and will dispatch experts for positive identification. They also enforce the federal and state quarantine regulations that govern the movement of certain materials.
Regulated items that cannot be moved out of a quarantine zone without proper certification include:
- Soil
- Plants with roots and soil attached
- Grass sod
- Used soil-moving equipment
These restrictions apply to both commercial businesses and private individuals to ensure that the ants are not accidentally transported. Following these reporting and compliance protocols helps protect the state’s agricultural resources and public health.