Acrobat ants are a group of ants in the genus Crematogaster, which contains about 430 species worldwide. While different species will vary in size and color, they all share the common characteristic of having a heart-shaped gaster (abdomen) connected to the thorax by two nodes.
Other ants have their node(s) connected to the ventral side (bottom) of their gaster, while acrobat ants have them connected to the dorsal side (top) of their gaster. This arrangement gives the appearance, when viewed from the side, that the abdomen is upside-down. It also allows the ant to raise its gaster up in the air in an almost scorpion-like position as a defensive posture. They can point the tip of their abdomen in any direction and squirt formic acid at their enemies. So not only can they perform acrobatic tricks, they also wear the squirting flowers normally worn by the circus clowns.
True to their name, acrobat ants are mostly arboreal, nesting in trees and other high places. But they are opportunists, and colonies also can be found under items on the ground and other dark, moist sites. They like to nest in protected places and often will occupy galleries in wood previously created by carpenter ants, termites or decay fungi. They typically do not cause further damage to the wood, but will clean out debris left over from the previous tenants and drop it in small piles. This behavior causes some people to believe they are dealing with a carpenter ant issue and use materials designed to treat carpenter ants, but it does not work to eliminate acrobat ants.
Acrobat ants also will occasionally nest in Styrofoam insulation material. Like termites, they easily can tunnel through this soft medium, create galleries and nesting sites, and be totally protected from the elements. Controlling acrobat ants in these situations can be a circus trick at times, especially when the Styrofoam is located in inaccessible areas, such as in the insulation of a vaulted ceiling. I have been involved with a handful of these cases and they are no gag (to continue with the circus lingo).
HIGH-WIRE ACT. In one instance, I received a call from a PMP that needed help with a particular situation. A customer was consistently finding little piles of blue “stuff” in several places throughout the house. They were on the bed, the living room TV, the kitchen table, on the floors and several other places. She cleaned it up, only for it to reappear after a day or two. Nothing else is seen, no pests, just piles of blue stuff. I asked for a sample of this blue stuff so I could examine it. Under the microscope, it appears to be tiny pieces of blue Styrofoam along with bits and pieces of dead acrobat ants. Even when the ants are in pieces, seeing the unique heart-shaped abdomens is always a sure thing.
I made the trek to the Blue Ridge Mountains in western North Carolina to visit the acrobat ant-infested big top of a home. It’s a log cabin with a cathedral roof nestled into a mountainside. The owner gave us a tour, pointing out all the places where the blue debris kept showing up. Looking up at the high ceiling over these areas made me think that being a trapeze artist could help in being able to access it to inspect more closely. Or perhaps a very high ladder.
The customer, who was way more versed in construction than I was, explained how the cathedral ceiling was built and that there was no attic area or void. Under the hardwood ceiling was a layer of thick blue Styrofoam insulation, then the roofing material on top of that. While pondering how we could access where the ants were nesting, a question was asked about drilling small holes into the hardwood ceiling above where the insulation was being dropped and injecting a dust or foam insecticide. I explained that acrobat ants don’t always drop their trash directly below their nesting site. They can travel for long distances away from the main nest before dropping the debris. So, it’s kind of like the ring toss game. You may get lucky, but chances are you’re not going to ring the nest and win the prize.
That leaves bait as the only option. But where do you place the bait if no trails are found? They have to be getting their food and water from somewhere, and since they are not trailing inside, let’s see if we can find them on the outside. After circling the home a few times inspecting the outside of the house we found nothing. Not a single acrobat ant. Well, there’s only one other place we hadn’t looked: the roof.
We secured a ladder and performed a high-wire act on the pitched roof. The house had an attached porch with an almost flat roof attached to the main roof. Up there we noticed, at the junction of the two roofs, a pile of leaves and debris that had accumulated. We made our way over and lo and behold, there were trails of acrobat ants gathering resources provided by that debris pile. It supplied them the food and water they needed. It also provided us the means to access the ants and put out a gel bait that they immediately feasted on.
After a few days the customer reported that the piles of blue stuff stopped showing up. He also informed us he will make sure leaves and other debris on the roof will be removed on a regular basis to help prevent this problem from happening again.
Solving difficult acrobat ant infestations can be a juggling act, and without some patience and diligence, they can sometimes make you look like clowns.