Most social insect species that create large nesting mounds from excavated soil can be found in Africa, South America and Australia, but not so much in the United States. However, the Allegheny mound ant is one exception, as these ants create mounds above their underground nests that can be as tall as 4 feet and as wide as 8 feet. The dirt mounds absorb the sun’s rays, causing warmth to radiate throughout a nest. This warmth ensures that eggs and larvae will survive and develop properly. Unsurprisingly, Allegheny mound ants can become pests in residential lawns and in urban areas due to their mound-building activities.

Disturbing these mounds in any way will cause thousands of aggressive ants to erupt and attack humans. Avoiding this can be difficult when walking through lawns, fields and pastures where the sizable mounds are abundant. Perhaps worst of all, these ants spray formic acid on plant roots, resulting in massive vegetation loss. Small trees and shrubs located within 40 to 50 feet of a large mound are often killed, and trees as tall as 8 feet have been killed by the ants. Worker ants of this species may also seek out sweet-tasting human food sources within homes, but the ants generally feed on nectar-consuming aphids in order to satisfy their sweet-tooth. Allegheny mound ants can be found throughout the east and midwest, but they are most concentrated in the northeastern states.

Although Allegheny mound ants do not sting, per se, they will swarm onto and repeatedly bite humans who disturb their nests. These bites often break the skin, and to add insult to injury, the ants spray formic acid into the bite wounds that they inflict in order to cause extra pain. These incidents can be overwhelming due to the large size of colonies, which usually contain more than 10,000 workers after a couple of years, and mature colonies contain more than 100,000 individual ants. Many particularly large mounds can be found in Santuit Pond Preserve in Mashpee, MA, and they are not uncommon in yards and rural areas throughout the northeast. According to  Larry J. Dapsis, an entomologist with the Barnstable County Cooperative Extension, residents often call asking how mounds can be removed and how the ants can be controlled within yards. Some pest control sources claim the colonies can be eliminated by pouring insecticide directly onto mounds several times, but other sources state that only insecticidal dusts are effective at killing colonies. The ants always emerge to attack humans who apply pest control treatments to mounds, so treatments should always be performed by a professional.

Have you ever encountered a large ant mound?