Unfortunately ants are oftentimes overlooked, used as an age-old synonym for insignificance, but these little beasties are much more sophisticated, intelligent and have a much more substantial impact than we give them credit for.
There are over 200 species of Army Ants known to science, belonging to 5 taxonomic subfamilies found across Africa, Asia and South America. The most studied species of army ant are Eciton burchellii and Eciton hamatum, native throughout much of South America; from Argentina to Mexico. These species became representative of army ants because their remarkable behaviour could be observed easier in comparison to other species.
Ants usually colonise in vast underground networks, however E. burchellii colonies exhibit what’s known as legionary behaviour. In fact all species belonging to the subfamily Dorylinae, containing 28 genera, demonstrate this. Legionary behaviour is when the colony constructs an aboveground bivouac; a structure formed by workers arranging themselves into a temporary protective shell. Whilst the queen and eggs are protected, foraging parties are sent out to find food during the day. After around 3 weeks the eggs hatch and the entire colony enters a nomadic phase called a raid, moving continuously for 2 weeks, raiding in the day and moving through the night until the reproductive cycle starts again.
Flickr | Axel Rouvin
The collective efforts of individuals function so well that each colony is considered a superorganism. E. burchellii raids are orchestrated swarms up to 15m across and are so efficient they consume 30,000 prey items a day. This makes them one of the most efficient predators on Earth.
Despite the ravenous destruction of their raids many army ant species are considered keystone species due to the number of associated animals per colony. Various birds and insects take advantage of the raids, either using it for protection or as a source for food; feeding on the prey the ants flush out or leave behind. One species of army ant is estimated to have the most associate species of any known species on Earth; between 350 and 500 species are thought to rely on the raids of E burchellii.
Leaf Cutter Ants
Much like Army Ants, the term Leaf-Cutter Ants is a broad classification referring to 47 species of ant. There are only two genera under the “Leaf-Cutter” umbrella, Atta and Acromyrmex, yet the Attines are considered to be more advanced due to the high number of social classes within colonies.
Leaf-Cutter colonies are the largest and most sophisticated societies we know of in the animal kingdom other than ourselves. Numbering anywhere up to 8million individuals, these ants have a complex social hierarchy and are capable of building megastructures that, relative to their size, would rival any of the world’s major cities. A colony’s central mound can be over 100ft across, and have several other mounds within a 250ft radius. In total, the area of a colony can take up anywhere between 320 and 6,460 sq ft.
What makes these ants more remarkable is their ability to farm, being one of only 3 groups of insects to cultivate fungi. Over millions of years, Leaf-Cutter Ants have been able to engineer garden chambers to maximise yields and orchestrate themselves into an efficient workforce. This is where the hierarchy comes in. The social castes consist of minims, minors, mediae and majors, with each class having a specific role to play. Mediae are the main leaf cutting individuals who forage, cut and carry leaf segments back to the cultivation chambers to feed the fungus. Once close, minims, the smallest workers who tend to the fungal gardens, clean and prepare the leaf segments to make it easier for the fungus to digest. (Minors and Majors are dedicated to defending the colony, eggs and queen).
Wikipedia Commons | Atta Cephalotes | Sarefo | Own Work
Because the fungus Attines feed on evolved alongside the ants themselves, the fungus eventually lost its spores; their necessity negated by becoming fully domesticated. Both the ants and the fungus are therefore mutually dependent on each other. Leaf-Cutters are sustainable farmers too, knowing not to overexploit they rotate food plants regularly.
Leaf-Cutter Ants are also considered a keystone species for their effect on vegetation. The construction of their colonies enriches the soil making it easier for plants to grow, and the leaves they strip from trees allows light onto the forest floor, giving others a chance to grow.
Most, if not all, species of ant are ecosystem engineers whether it’s through predator and population control, soil management or being a linchpin in the survival of associate species. But, as average global temperature continues to rise, so too does the danger they face.
A recent study conducted in Massachusetts and North Carolina revealed significant behavioural changes in ant colonies in response to slight rises in temperature, observing the regression or complete shutdown of colonial behaviour and the retreat into underground nests.
The ecosystem services provided by ants affect entire ecosystems and, if lost, would carry repercussions for us, giving us yet another reason to commit to adequate climate action.