Acrobat Ants

Introduction

Acrobat ants include several species. Their common name is descriptive of this ant’s habit of raising the abdomen over the thorax and head, especially when disturbed. Various species are found throughout the United States, including at altitudes of up to 8,000 feet (2438 m).

Recognition

Workers monomorphic, about 1/16-1/8″ (2.5-4 mm) long; queens range up to 3/8″ (10 mm) long. Color light brown to black, sometimes multicolored. Antenna 11-segmented, with 3-segmented club. Thorax with 1 pair dorsal spines. Pedicel 2-segmented, attached to upper side of gaster. Gaster heart-shaped in dorsal view, broadest towards thorax and sharply pointed at rear. Stinger present. Workers of many species emit a repulsive odor when alarmed.

Similar Groups

1. 1. Leafcutting ants (Atta spp.) with 3 pairs of dorsal spines on thorax, pedicel attached to middle of gaster in lateral view, and gaster not  heart-shaped in dorsal view.
   2. Other 2-node ants with pedicel attached to middle of gaster in lateral view and gaster not heart-shaped in dorsal view.

Damage & Signs of Infestation

Often the only exterior indication of damage is the accumulation of debris expelled by these ants, especially if the debris is styrofoam insulation. They prefer wood softened by decay fungi or styrofoam insulation, but may enlarge cavities in wood made by other insects. They will occasionally strip the insulation from electrical or telephone wires which can cause short circuits.

Biology

Little has been published on acrobat ant biology. Most structure-infesting species are described as nesting in moderate to large colonies. Probably the most commonly encountered species is C. lineolata (Say) with workers 1/8″ (3-4 mm), males 1/8″ (3.5-4 mm), and females 1/4-3/8″ (7-8 mm) long. This species varies greatly in color and nests up to 5,000 feet elevation (1,700 m) in the Blue Ridge Mountains. Many of the species, including C. lineolata, tend aphids and will build carton sheds to cover them. Similar sheds are built by C. lineolata and used as brood/rearing chambers. Swarmers have been observed in nests or swarming from mid-June to late September; in North Dakota on July 18th, in Colorado from July 4-August 5th. The odor emitted by C. lineolata resembles mammalian feces.

Pest Control

Inspection is the key to successful control and the inspection methods are similar to those used for carpenter ants. When workers are found indoors, the first place to inspect is the structure’s exterior. Look for these ants on plants infested with honeydew-producing insects; treatment of such plants may help solve the problem, but usually requires a lawn and ornamental license. Also, look for trailing ants on the foundation. If siding is present, look for bits of foam insulation which would indicate a nest behind the siding. Check for trailing ants on all wires, utility lines, and pipes coming into the walls and on tree/shrub branches in contact with the wall. Look for signs of excessive moisture such as peeling paint along soffits, around window frames, etc.; a moisture meter is useful.
In the yard check logs, stumps, firewood, tree cavities, dead tree limbs, and loose bark for ant nests. Also inspect under rocks and debris lying on the ground for ant nests. Inside, inspect areas with present and past histories of excessive moisture. Be sure to ask the customer about past water leaks, plumbing problems, etc. A moisture meter is  useful to confirm/detect areas of high moisture. Inspect areas of old termite and carpenter ant damaged wood for acrobat ants. Sometimes an electronic stethoscope can be useful to help locate nests.
Inside, a light application (misting or spritzing) of a nonrepellent pesticide directly onto the foraging trails of ants is often required. This will usually give results in a few days at most. Be sure to cover any surfaces below the application site with plastic before application to avoid unwanted contamination. Such an application will usually take care of the problem. However, if the ants persist, first inspect to be sure that you did not mistreat a foraging trail of ants. Then try any or a combination of the following 3 treatment strategies:

1. Nests located in wood can be treated by wood injection. Drill into the wood until galleries are intercepted, then inject pesticide via a high-pressure aerosol or dust. Nests in wall voids can be treated by gaining access via electrical outlet and plumbing installation holes and injecting dust (better) or an aerosol insecticide; drilling a small hole into the wall just above the baseboard is a last resort choice for void access. Nests located in wallboard behind siding require that the siding first be removed by the customer or a contractor. Exposed nests can be vacuumed away while nests in wallboard will require treatment via aerosol or dust injection.
2. Acrobat ants that are foraging from the outside can be kept out by sealing cracks and crevices followed by spot treatment of where utility lines etc. enter the wall. Tree and shrub branches should be trimmed back. A full perimeter treatment may be necessary using nonrepellent pesticide. Be thorough and include treatment up under the siding-to- foundation wall junction if such is present.
3. If ornamental plants and shrubs are infested with aphids scale insects, and/or mealy- bugs, the customer should have these treated to discourage acrobat ants.