From Dr. Eleanor's Book of Common Ants
A.K.A.: The Asian needle ant
Size: workers: 0.2 inches, queen 0.25 inches
Where it lives: In forests, Asian needle ants nest in rotting logs, under leaves and mulch, and under rocks. In human environments, Asian needle ants can nest anywhere from potted plants to under door mats, in landscaping materials, and under dog bowls.
What it eats: While it loves termites, Asian needle ants will eat pretty much anything it can find, from dead insects to other ants to human garbage.
What’s the Big Deal?
The Asian needle ant (a.k.a. Brachyponera chinensis or Pachycondyla chinensis) reminds me of a ninja superspy. Sleek, sneaky, and all dressed in black, ninjas, at least in bad movies, are masters of disguise and inevitably up to no good. The same holds true for the furtive Asian needle ant; this stealth operative is sneaking across forests and backyards throughout the eastern United States.
Asian needle ants originally snuck into the United States from Japan (Yashiro et al. 2011). Nobody knows how they got here, but they have been moving log to log since at least the 1930s (Smith 1934). Slender, shiny, and black with lighter orange legs, Asian needle ants look like they are dressed for subterfuge. At about 0.2 inches long, one worker is almost as long as a kernel of un-popped popcorn.
Asian needle ants aren’t fussy when it comes to where they make their home. In the woods, Asian needle ants nest in logs or under rocks and leaves. Sometimes their nests look like caverns connected by tubes and stuffed with eggs and ants. Other times they look like nothing more than a group of ants hanging out. Around human structures, they nest anywhere from potted plants to piles of mulch, and even underneath door mats. Colonies can have anywhere from a few dozen workers to a few thousand, and those workers can live in one big nest or many small ones.
The Asian needle ant’s distinctive walk is a dead giveaway of its identity. While some ant species lift their legs high and prance around or stomp their way to and from their nests, Asian needle ants, hunker down close to the ground and creep with deliberate, stealthy steps. Like ninjas, they move alone; they never follow the trails of their sisters as they don’t know how.
It’s easy to confuse Asian needle ants with wood ants, as both are medium-to-large and black, but one distinguishing characteristic separates Asian needle ants from wood ants (and ninjas, for that matter): They are clumsy and terrible climbers. If you trap an Asian needle ant in a glass jar she won’t be able to climb to the top like other ant species and will instead wander helplessly around the bottom of the jar or run in place like a startled cartoon character. Be careful if you try that trick because Asian needle ants can sting the tar out of you (Nelder et al. 2006).
A Stinging Sensation
As an entomologist who spends a lot of time studying Asian needle ants, I’d heard of the horrors of their sting prior to experiencing it for myself. The day the first sting happened, I was digging around with bare hands into a log I hoped was infested with them. It was. As I reached into the log to pull off a chunk of wood, I accidentally closed my hand on an Asian needle ant nest. A startled worker stung my palm. Because I had read that two-to-four times as many people are allergic to Asian needle ant venom than are allergic to honey bee stings, my alarm seemed justified. Based on those reports, I was afraid my hand might fall off, but nothing like that happened.
At first, I felt a slight burning sensation right where she stung me. About an hour later, the burn spread out to an area about the size of a quarter around the sting, and it began to feel a little like being stabbed with pins. This flash of sharp pain followed by a dull nerve ache continued for the next two weeks every time I touched the area around the sting. For those of us not allergic to Asian needle ants, that’s the worst part of Asian needle ant stings. I’ve been stung innumerable times since then, and it’s almost always the same.
While Asian needle ants have pricked me many times over the last few years, I don’t blame any of them for doing it. Unlike the war-mongering fire ants, which eagerly attack en force, stinging anything they can get their angry little tee-hineys on, Asian needle ants prefer a more peaceable lifestyle and sting only in self-defense as a last resort. Every one of my stings occurred when I put pressure--whether on purpose or by accident--on the worker so she poked me with her stinger to get away.
What’s for Dinner?
Most of the time, Asian needle ants use their stinger to subdue their favorite food: termites. Watching an Asian needle ant around termites is like watching me at an all-you-can-eat buffet. She gets very excited, running around grabbing every one she can. Practically defenseless, termites have thin, soft exoskeletons and are juicy treats for any meat-loving insect. When an Asian needle ant stings a termite, she grabs it in a bear hug and jabs her stinger deep inside. Her venom paralyzes the termite but does not kill it (Bednar, unpub. data). By keeping the termite alive, she can stockpile it in her nest without worrying about its rotting before she and her nestmates get a chance to eat it.
Asian needle ants love termites, but they aren’t picky eaters. If you see one out and about, she is probably scavenging the ground for other ants, dead and dying insects or even human garbage. Unlike other ant species, Asian needle ants do not follow foraging trails. If one finds food too big to bring back to the nest, she will run home and tap one of her sisters imploringly on the head. Her sister responds by folding up in the fetal position. The forager then picks her sister up, tucks her under her body, and creeps as fast as she can back to the food. They’ll work together to bring the food back or go get more sisters to carry over to help (Guenard and Silverman 2011). Like ninjas, Asian needle ants are masters of disguise and sometimes sneak into other ants’ nests undetected, killing workers. They steal back to their own nests with ant bodies in their mandibles. Then, the feast begins (Spicer Rice, in press.).
Their Covert Operation
The Asian needle ant ninja army has a stealthy mission worthy of our attention: to steadily disassemble forests across the United States. When Asian needle ants move into a forest, other ant species like winnow ants, acrobat ants, little black ants and thief ants all pack their bags and move out, pulling the forest apart at the seams (Guenard and Dunn 2011, Rodriguez-Cabal et al. 2012). Asian needle ants make life miserable for other species. They eat them or their food and take up space native species use for nesting.
“Why should we care if a few ant species go missing?” you might ask. “All ants do is ruin my picnic! We could do with fewer of them anyway!” Let’s take a closer look.
Picture a car factory where everybody has his or her special job. One person puts on the windshield wipers, another the wheels, while another is responsible for the engine and another adds the finishing touches like door handles. They all work together to build a beautiful, well-oiled machine. Suppose one day the company hires a new employee to add a new gadget in the car. This employee gets paid a lot of money, so much money the company has to lay off the windshield wiper person, the wheel person, and the engine person. They even kick out the door handle guy.
Here’s the problem: while this new employee is really good at gadgets, he doesn’t know anything about engines or door handles. You can forget the windshield wipers and wheels. What kind of car will this car factory produce without their employees? One that won’t even roll!
Our forest is a lot like the car factory. While some of us might think of ants as pesky, most ant species help keep the world rolling along. In fact, of the more than 30,000 ant species in the world, less than 0.3% are pests. The rest have valuable jobs, and we need them to show up for work each day. Take some of the species Asian needle ants displace, for example. Acrobat ants and thief ants help keep the forest canopy healthy by regulating tree pest populations. Aphaenogaster ants move seeds across the forest floor, controlling the distribution of forest plants and promoting healthy forest herb diversity and growth. Little black ants turn the soil, aerating it to keep the trees and shrubs happy. Taking away all these species and replacing them with just Asian needle ants can spell trouble for forest health.
Asian needle ants, those little ninjas infiltrating our turf with their clandestine movements and veiled operations, are a force to be reckoned with here in the United States. Our ants and forests aren’t prepared to battle this stealthy foe. They need us to help them fight back. You and I can use our knowledge to spot them and work to kick them out. We can let people like the folks at School of Ants know when we find them, so they can track their movements across the U.S. and research ways to keep them at bay. Asian needle ants might be ninjas, but you and I are a citizen army. Together, we can beat them.