The Battle for the Great Acacia [Part 1]

Introduction: Vachellia cornigera is a type of Acacia tree commonly known as a “myrmecophyte.” The term ‘myrmecophyte’ refers to its symbiotic relationship with ants. Pseudomyrmex ferruginea is one of these ant species that has built a relationship with the Acacia tree, and this particular ant species is one of the most fiercely protective ant species in existence. Thus, the tree relies on the ants for protection while the ants rely on the tree for habitation and food. To illustrate this complex and epic relationship that has continued to grow and evolve over time, I have decided to write a short fiction story about it. Though the story you are about to read is ‘fiction,’ the science behind this relationship is very real. Though the ants and other living things do not possess conscious thought, the actions they take in this story are plausible. Every aspect of the ant-tree relationship depicted in this story is factual. I hope that, through reading this story, you will gain a greater appreciation and understanding for how co-evolution works and just how intricate and amazing these symbiotic relationships can be. Perhaps you, the reader, will even become inspired by this relationship, as I have. Now, on to the story.

Myrmex had just been appointed commanding general of the colony by the queen herself. This had been her dream ever since she was a tiny larva. This great honor was given to her after the former commanding general had been decapitated by an attacking centipede. Leading the colony of more than 4,000 ants and defending the great acacia tree was no easy task. Especially this acacia tree–the Great Acacia tree! But somehow, Myrmex felt like she was born for the job. Other acacia trees had grown in the area and were now being run by neighboring ferruginea colonies. But this particular acacia tree that Myrmex calls home was the first in the area that had been settled by her ancestors. The relationship between ferruginea and the Great Acacia tree has deep roots, and the story of its birth has been passed down from generation to generation. Myrmex knew the story by heart.

Deep in the wet lowlands of Central America, a competition for space and resources was under way. For a plant, that meant growing tall and spreading wide to soak up as much of the sun and other resources as possible. For smaller trees, there was only one solution–adapt or die. Fortunately for the small tree Vachellia cornigera, natural selection (the driving force of evolution) had some tricks up its sleeves. When a ferruginea worker from a young colony of ants had stumbled upon the thorny, inhospitable little tree, the birth of a beautiful relationship had begun. The worker ant climbed the little tree and found that the sweet nectar the tree abundantly produced was more than enough to supply her colony with food for days. She also discovered that the nasty looking thorns were actually hollow and would make great homes for her colony members. Plus, they would deter natural predators of her species. She quickly alerted her colony of the new home and they vowed to defend it at all costs, much to the joy of the Great Acacia tree. The ferruginea colony continued to defend the tree from animals and plants alike, and the tree in return would provide the ants with more and more food as well as homes. That ferruginea worker who discovered the Great Acacia tree was Myrmex’s direct ancestor.

As Myrmex reflected on the history, she exited her hollow thorn home and marched up the trunk of the Great Acacia tree towards the Queen’s chambers. The sun’s rays danced on the green acacia leaves and painted the tree a golden hue. The Great Acacia tree, majestic in the sun’s light, stood proudly with hundreds of orange ants dotting its surface. Like a royal court with its noble courtiers busily maintaining the kingdom.

As she climbed up the trunk, she passed many fellow soldiers who would rub their antennae together and use them to tap her on the head, this was a sign of respect. Other soldiers would pass by and release pheromones (chemical signals or messages) which Myrmex interpreted as, “what are your orders general?” Myrmex decided to leave a pheromone scent of her own all the way up the trunk, “I am going to receive orders from the Queen right now. Standby.”

As she crawled across a thick limb towards the top of the tree, she passed multiple worker ants harvesting beltian bodies-special packages of sweet nectar provided by the Great Acacia tree as thanks for our protection. The beltian bodies were fastened to the edges of each individual pinnule of the acacia leaf, reddish nutrient-rich drops that glistened in the morning sun. As Myrmex marched by the workers, one worker approached her and offered her a sampling of the fresh nectar. The general let the sweet juices soak into her mouth parts, a few drops running down her mandible. Satisfied with the nectar, the general tapped her front two feet against the branch, a signal for the workers to transport the nectar directly to the Queen’s chambers. The workers gathered as much nectar as they could and followed behind Myrmex to the thorn of the Queen.

The Queen’s thorn was larger and sturdier than most and was tucked away on the underside of a large branch. Being towards the top of the tree, along with it’s obscure location on the branch and sturdy structure, the Queen’s thorn was rarely disturbed by outside threats. Upon entering the Queen’s thorn, Myrmex noticed the Queen attending to her eggs. It must have been a new clutch because Myrmex did not recognize some of the eggs. The workers that followed Myrmex into the thorn delivered the nectar to the Queen. The Queen happily began eating the nectar and used a single antenna to point to some eggs in the corner of her chambers. The workers immediately began gathering eggs to take to the larva thorn.

“Welcome general I have been expecting you,” Myrmex had interpreted the Queen’s pheromones upon entering the thorn. The Queen, about three times the size of Myrmex, sat in the middle of her chambers resting on her oversized abdomen while devouring nectar. Myrmex rubbed her antennae together and used them to tap the Queen on the head, a sign of respect, royalty, and submission.

The Queen put out a new pheromone.”You will bring great honor to me, to your colony, and to the Great Acacia. Spring is upon us, and with spring comes invaders seeking to steal away the Great Acacia’s nectar. Your first task will be to defend our home from these invaders,” Myrmex used her antennae to interpret the pheromone.

Myrmex responded by slowly rubbing her legs together. The Queen felt the vibrations and interpreted the message. The Queen sent out vibrations of her own along with a series of head nods, “No need to worry, the colony will be just fine with you leading them. I am getting old and pretty soon a new Queen will take my place. But you do not need a Queen’s guidance to defend the Great Acacia or your fellow ants. You have my trust. Now go and prepare the colony for the spring invasion. I will do my best here to provide you with fresh new soldiers.”

With that, the Queen stood up gingerly and continued to tend to her eggs. Myrmex tapped her feet against the ground, thanking the Queen for her confidence in her, and exited the thorn.

With renewed confidence, along with a little anxiety, the general marched up and down every branch of the Great Acacia spreading a specially prepared pheromone. A special message to her troops, “Spring is upon us. The spring invaders will be at our thorn-steps before long. I want soldiers patrolling every branch of the Great Acacia starting tonight and into the morning. When invaders are spotted, sound the alarms and charge at the invaders. Eat well, rest up, and get ready to show those invaders the strength of a ferruginea army.”

Myrmex spent a tense, sleepless night reviewing combat strategies in her head for every possible assailant that could invade their tree. As a normal soldier ant, she would not have lost a wink of sleep before a big spring invasion. But being the general, she felt intense pressure to lead her troops to flawless victory.

The next morning came with a swift shaking of a lower tree branch followed by a pungent pheromone warning cue. Myrmex rushed out of her thorn to see a long, glistening black segmented body with roughly two hundred thrashing legs. Their first spring guest was a centipede, and a big one at that.

With slight apprehension, the former ferruginea general being decapitated by a centipede after all, Myrmex jumped off the branch and plummeted toward her target. Landing on the upper trunk of the centipede, Myrmex unleashed a series of stings on the back of the centipede and began chewing off some of its legs. The centipede writhed in pain but maintained a steady course towards the Great Acacia’s sweet nectar. At this point, the swarming pheromone was in full force and many ant soldiers had come to the general’s aid.

After a few more stings and limb-hackings, the centipede finally curled into a stiff ball and tumbled off the tree. Myrmex felt energized, killing a centipede while remaining unscathed seemed to be a good omen for the new general. But the victory was short lived. Alarm pheromones and intruder vibrations were occurring from multiple sources at this point. Myrmex and her squad marched swiftly toward a not-so-distant relative of theirs–the wasp.

Her squad had to withstand multiple wasp stings and the hymenopteran jaws of death to defeat the winged intruder. Clipping the wings off the wasp, multiple stings to its head, and throwing it off the tree did the trick. The whole tree had seen action that spring morning and with every battle the ants had seen victory, not without some casualties of their own.

The final alarm pheromone came from a source of great concern to the general. A rather large intruder had been spotted near the Queen’s chambers. If the intruder finds its way to the Queen’s chamber and decides to eat the Queen, that could lead to the eventual end of the colony. Without the Queen, no new ants would be produced and without the rising generation of ants, the colony and even the Great Acacia tree may die.

Myrmex and her squad marched frantically to the Queen’s thorn, all the while leaving an urgent pheromone message to other soldiers, “All soldiers make your way to the Queen’s chambers at once! The Queen is in danger!” As Myrmex neared the Queen’s home, she passed a soldier ant grabbing a nectar snack from a nearby leaf. The general was outraged at this but didn’t have time to scold the soldier, so she released a stronger dose of that urgent pheromone message near the slacking soldier.

As the squad reached the site of danger, they halted in pure terror. What stood before them this time was not an invertebrate. A bird hopped along the branch, pecking at thorns trying to reveal the ant snack inside. The Queen’s thorn was inches away, on the underside of the branch directly below the bird’s feet. In grotesque horror, the general’s squad watched as the bird broke open a nearby thorn and began eating innocent ant larva inside. The squad charged.

While the bird munched on helpless ant larva, the soldier ants made a decisive first strike. Myrmex led a small group up the bird’s legs and into it’s feathered body, stinging the bird repeatedly, while a larger group swarmed the bird’s feet immobilizing and confusing the bird. A smaller group of soldiers surrounded the Queen’s thorn as a safety precaution. The bird staggered, but shifted its focus to the stinging ants.

Peck, one of the general’s nearby soldiers was gone. Peck, this time a soldier directly adjacent to Myrmex was gone. Myrmex charged up the dorsal side of the bird towards it’s head. Peck, this time some ground units were eaten. Myrmex landed a series of stings directly on top of the head of the bird. This attack seemed quite effective as the bird shrieked and flew backwards off the branch. Shaking its head vigorously, the bird circled back for a second attack on the ant swarm. The general, hanging on for dear life, regrouped and made her way to the bird’s eye. Landing a successful sting to the eye, the bird let out a piercing cry. Briefly landing on the branch in a daze, the bird prepared to retreat. Myrmex and the other bird-riding ants used the opportunity to jump off.

Watching the bird fly away, the colony stamped their feet simultaneously while rubbing their legs together–a victory cheer. Myrmex knew smaller invaders would be coming for hours to come, but this seemed like a turning point in the spring invasion. A moment worth reveling in.

Out of the corner of her eyes, Myrmex spotted the slacking soldier ant still eating away. Rage returning, she marched toward the defected soldier. How could a fellow, noble ferruginea sit back and eat while its colony mates were dieing in battle?! As she neared, she did not recognize its pheromone signals. All of a sudden Myrmex thought this ant looked hairier and slightly bigger than a normal ferruginea. Just then, the soldier defect jumped high into the air, higher than any ant ever could, drifting towards the earth below. Myrmex noticed a silky stand trailing behind the defect, making its decent slow and decisive. The general knew they were now dealing with a new kind of invader. A mimic.

 

Thank you for reading my first installation of my short fiction story “The Battle for the Great Acacia.” If you enjoyed reading it, or if you have any questions, drop me a comment. I would love to hear about your reading experience! Stay tuned for the part 2 of this story within the next couple of weeks.

 

Sources if you are interested in learning more about the ant/acacia relationship. I used information from many of these awesome sources!

• https://www.sciencedaily.com/releases/2014/01/140115113243.htm
• https://www.sciencedaily.com/releases/2009/10/091012121331.htm
• https://www.antwiki.org/wiki/Pseudomyrmex_ferrugineus
• https://phys.org/news/2019-07-mutualistic-relationship-ants-acacias.html
• https://omnia.sas.upenn.edu/story/mutualistic-relationship-between-ants-and-acacias