Workers are dimorphic (major and minor workers). The BHA receives its common name from the large-sized head of the major worker, or "soldier." Minor workers are small (2 mm) reddish brown ants. The majors are much larger (3 to 4 mm), but only constitute about 1% of foragers. The front half of the major's head is sculptured, while the back half is smooth and shiny. The petiole (waist) of both worker forms is two-segmented and the post-petiolar node is conspicuously swollen. The antenna is twelve-segmented with a three-segmented club. The entire body is covered with sparse, long hairs. Workers have a pair of short propodeal spines (spines on waist) facing almost directly upward. There is usually a dark spot on the underside of the gaster.
Egg, larva, pupa and adult
Trails of foragers can often be observed along trees trunks, sometimes climbing into canopies of tall trees. Similar trails might be seen on the exterior walls of structures as ants climb into attics or other natural or artificial voids.
Trophallaxis (an exchange of food between ants) is frequently observed between two minor workers, or a minor and major worker.
The BHA can be found nesting in disturbed soils, lawns, flowerbeds, under objects, such as bricks, cement slabs, or flower pots, around trees or water pipes, along the base of structures, and walkways, where displaced soil is usually observed from the action of ants digging below the surface. Well-cared-for lawns may have BHA infestations that are less noticeable, except along the edges where lawns meet walkways where piles of soil are often deposited. BHA populations expand into neighboring areas by following along these lawn-walkway edges or roadways. Population movements into new areas to establish nests and subsequent displacement of other ant populations can be rapid.