There’s a New Material in Town – Introducing the Curious Fire Ants

There is more to an organism than meets the eye especially when its scientific name ‘Solenopsis invicta’, is literally translated to ‘undefeated’, or ‘invincible’. Hence, they rightfully deserve a spotlight in today’s article where some of its mind-blowing and astonishing capabilities of these six-legged critters are explored.

The term Fire ant does not actually represent one particular species, but collectively refers to more than 280 different species of ants all under the Solenopsis genus. They were bestowed this evocative name due to their distinctive appearance: a vibrant reddish-brown colour spans from the tips of their antennae to the edges of their thorax, followed by a dark brown or black abdomen. They’re also called as such because, despite their small size, their sting is famous for being extremely painful even to adults, with the intensity similar to that of a fire burn.

As we know, honeybees die when they use their stinger because there are two barbed lancets protruding from it. These lancets hook and latch on tightly to the skin so when the bee tries to pull away, their digestive tract (connected to the stinger) ruptures and parts of it are left behind together with the stinger. However, this is not the case in fire ants, since they do not have the same lancets and are able to retract their stingers at will, thus stinging repeatedly in a short period of time. The ants first bite with their pincers to get a good grip, and then inject an alkaloid venom named solenopsin through their back stingers—which is responsible for the fiery sensation, may cause hives to break out, and even death from anaphylactic shock in people allergic to the chemical.

Source: AskABiologist

The invictus is classified as a highly invasive species because they have the ability to adapt quickly and survive in a multitude of extreme environmental conditions. For example, abilities include: being ‘immune’ to floods, able to live both in grassy rural areas as well as the city, Queens producing up to 1600 eggs per day, and having a wide-ranged, omnivorous diet consisting of germinating crop seeds, young trees, sap, and are especially attracted to fats, as in birds, small animals, and both adult and larvae of other insects.

One interesting fact is that not only are these ants capable of brute force, but also strategic calculation. They tend to form mutualistic relationships with aphids, and species of Lycaenidae and Riodinidae butterflies. Protection is offered; fire ants either serve as ‘soldiers’ to fend off predators, or ‘engineers’, to construct shelters for their larvae. In exchange, they are fed honeydew or sugary fluids that these species produce.

Source: ArcsTechnica

Due to this aggressive vitality, they have successfully driven several local species such as the Euglossa imperialis (bee) away from their habitat, and sometimes even to the point of endangerment. Today, they have spread to more than 40 countries around the globe, through means of: travelling 1 to 12 miles during their mating flights, floating downstream when there’s heavy rain, carried along in uplifted soil, or even settling in all kinds of transportations like cars, trains, ships etc (the females have a tendency to be attracted by shiny, metallic objects!).

Did you know that when fire ants join together you could grab a handful, coax them into a round ball shape, then poke, squeeze, pat and bounce it just like a rubber ball?

And except for that one or two occasional ant who would get fed up with your patting and decide to leave the clump, the rest would still remain perfectly in shape and elasticity just like toy slimes? 

Surprisingly you could juggle, and even throw the clump with sufficient force, yet it would not break apart and make a splattered mess (although it is highly un-recommended, for the sanity of anyone around you, and thus should only be conducted in experimental set ups and controlled environments).

If you have ever ushered a colony of fire ants into a bucket, then proceed to pour water into the bucket, just reach in with a shovel and you’d observe that the viscosity and fluidity of the ant clump is no different from the behaviour of fluids such as thick gravy (or just water).

This adaptive feature seems to be innate, since both colonies bred in captivity as well as wildfire ants demonstrate this.

These self-aggregated rafts are waterproof and floats because ants have a hydrophobic exoskeleton–which would repel water molecules–as well as a layer of small hairs that could trap air bubbles around the body to increase buoyancy. An individual ant may struggle but collectively they can drift up to weeks with no problem. And yes they bring their entire family along, with high protection priorities given to the queens and larvae.

An ant’s leg is divided into 3 segments: the Tibia, Tarsus, and Pre-tarsus, with small hair-like spikes protruding from each segment. Each ant ‘hold hands’ with other ants around them by locking onto each other’s leg spikes and this greatly amplifies the aforementioned abilities. The greater distribution of bubbles form larger air pockets to serve as an oxygen supply for ants at the bottommost layer, and if they ever sink below water, they’d ride it like an elevator back to the surface to rejoin the raft. This cohesive strength has the same concept as hydrogen bonding in water molecules, and is so strong that it would not break the surface tension of the water despite ants being denser than water. Therefore if you pressed a raft, they would bend downwards without breaking then bounce right back—again, viscoelastic.

Source: GeorgiaTech

Source: LiveScience

Utilizing the above mechanisms, fire ants are also highly organized architects. In a rain, where water droplets fall vertically from the sky, these ants build an ‘Eiffel tower’ to repel water. The ants in the inner layer would be protected, while the slanting outer layers could increase the sliding movements of water molecules down the ‘walls’ rather than sinking and collecting between the ants. There would always be more ants on the bottom than the tip because each ant can only withstand the weight of three of its brethren, not more. Coincidently, this follows the ‘principle of equal load-bearing’, and is the same concept implemented in the Eiffel tower’s construction.

Source: ScienceNews

However, when there is a greater accumulation of water like a flood, the ants would spread out evenly like an ink drop, taking the shape and form of a pancake.

Source: ScientificAmerica

But how do fire ants know what to do? Are they taking orders from a higher up like the queen? Do they discuss with each other and correct confused ants to their designated positions?

Turns out that they take no instructions and have no leader. Each ant is the master of itself. And most surprising of all, ants accomplish all these while not knowing the exact actions of their brethren. Although ants are blind, they have an acute sense of touch and smell. They detect stimulus and navigate the environment based on these senses, and turn this information of relativity into just three simple rules, which is used effectively time and again, to build all of the structures and mechanisms presented above.

1. If ants are moving above you, don’t move.

2. If not, move randomly in any direction, and don’t stop.

3. Only stop if you find a space next to at least one ant, which are not moving. Squeeze in; fill up space, and link up.

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