The ants inject formic acid into surrounding plants, killing small trees and shrubs.

Members of the formic acid producing genus Formica are known for their citrus taste.

[2] The Allegheny mound ant's appearance is very striking: both its head and thorax are red-orange; its gaster is black-brown.

In the Northeastern United States, Allegheny mound ants (Formica exsectoides) are credited with causing lesions typically in the form of a deep constriction about 10 cm long on the main stem of small individuals of a variety of species, both hardwoods and conifers, including white pine and Scots pine.

No live trees or shrubs of any height occur in close proximity to the mounds.