Of termites and air-conditioning…

Of termites and air-conditioning…

The African Savanna is a fascinating place. The delicate web of life has existed for millennia and continues to play out on a daily basis. It is complex and bewitching, providing endless content for the blue-chip nature documentaries which abound. The intricate links have layer upon layer of connections, weaving a spellbinding tale of life and death. From large, ferocious mammals to barely visible critters – each has their own unique story. One of the most interesting is that of the termite – and our specific focus in this article is on the fungus-growing termites. 

The order name Isoptera originates from the fact that the imago (adult) has wings of equal size (‘Isos’ in Greek meaning the same and ‘ptera’ meaning wings). The insects of Isoptera are commonly called termites in English. There are between 2500 and 3000 species of termites in the world (accounts of numbers vary), and Africa with more than 1000 species has the richest intercontinental diversity. They are often referred to as ants which they are not.

Termites, cockroaches and mantids all share a common ancestor that crawled the earth about 300 million years ago. Fossil records show the earliest actual termite specimen date back to the Cretaceous period (about 145 to 66 million years ago). A termite is also the record-holder for the oldest example of mutualism between organisms. A 100-million-year-old termite with a ruptured abdomen was found encased in amber, along with the protozoans that lived in its gut. Which leads us to why they are important.

Termites play a huge role in organic decomposition. Their food is primarily cellulose, which is obtained from a wide variety of decaying plant material e.g. wood, grass, leaves, humus (dark, organic material that forms in soil when plant and animal matter decays), manure of herbivorous animals, and materials of vegetative origin. They also feed on fungi growing on decaying plant material. Try imagining a world where decomposing materials were not processed?

The termite gut is full of microorganisms capable of breaking down this cellulose. This symbiotic relationship benefits both the termites and the microorganisms living within their insect hosts. The termites house the bacteria and protozoa and harvest the wood. In return, the microorganisms digest the cellulose for the termites. Termites are one of the most efficient cellulose-digesters, with assimilation efficiencies often approaching 99 %. They break down these tough plant fibres, recycling them into new soil. These hungry insects are thus vital to the health of our ecosystems. As they tunnel, termites also aerate and improve the soil.

Termites are considered a keystone species, i.e. an organism that helps hold the system together. Without them the ecosystem in which they live would be incredibly different – or may even cease to exist. They are highly social and abundant, representing a disproportionate amount of the world’s insect biomass, and around 10% of all animal biomass in the tropics. The numbers of termites in the savanna system can also be quite extraordinary – in fact, their biomass can exceed the biomass of all the mammals in this ecosystem. By weight of numbers alone, it makes sense that they must have a massive impact on the system.

Termitaria are the nests of termites (housing an entire colony of up to several million individuals), built from clayey soils brought from beneath ground level and mixed with termite saliva, resulting in their concrete nature. These structures are typically 2 to 3 metres high. The tallest termite mound recorded was a 12.8 m high mound found in the Republic of Congo (Guinness World Record). The “living space” beneath each mound in the savanna system covers approximately 50 square metres. What is often seen as simply a lump of clay on the landscape is a highly efficient, complex architectural masterpiece.

The term “swarm intelligence” is defined as a ‘collective behaviour of a decentralized or self-organized system’. These systems consist of numerous individuals with limited intelligence interacting with each other based on simple principles. Nowhere is this more apparent than the collective efforts of termites when building their nests. They are well known for their ability to regulate the environment of their nest such as temperature and humidity. Large colonies (with mounds above 2 metres) of termites are able to attain constant nest temperatures of approximately 30 °C that are largely independent from ambient temperatures and optimal for the growth and development of the termites and their fungi. A spiralled mound consisting of a network of vents and tunnels set around one central chimney enables fresh air to circulate throughout the system. These tiny insects are able to teach human engineers a thing or two about an elaborate air conditioning system. There are many factors which come into play in achieving this – please see additional articles in info block if this interests you. 

Fungus-growing termites cultivate a very specific fungi (of a genus called Termitomyces) for food in their colony. They cultivate the fungi to digest cellulose which they are unable to digest. Dead plant material is brought into their nests and provided to the fungus as a growth substrate. The fungi and the plant material are both consumed. When the spores ‘escape’ the nest, they are often found growing on the outside of the termite mounds and make a delicious treat for humans.

The colony includes different castes, all with specific roles. Each type of caste looks different, but they are genetically identical. Kings and queens (that may live up 20-50 years) are responsible for reproduction. The termite king and queen mate regularly, resulting in up to 30,000 eggs being laid each day. A queen termite runs the colony using chemical signals (pheromones), which are exchanged across the colony by the sharing of food and saliva. These signals may prompt her to produce termites of a certain caste, e.g. more soldiers if many had recently been killed. The soldiers are obviously for defence, workers for general tasks and alates establish new colonies. Termites swarm after their original colony has reached a certain capacity level and is ready to expand. For most colonies, this happens once a year, the timing of which is governed by a complex set of requirements. Rainfall is the primary stimulatory factor triggering flight. The threshold temperatures for swarming seems to be between 17–19°C – if the air temperature drops below these figures, the flights are generally aborted. Windless conditions are favoured so that the alates are not dispersed too widely resulting in the males and females not being able to find each other. Flight times are also governed by light intensity and take place at dusk (low light intensity). The most interesting fact about these flights is that the vast majority occur with a waxing moon.

I truly believe that we are only at the very early stages of understanding this incredible planet on which we live. Every discovery leads to another, and as we continue on our quest for knowledge, we uncover further intricate links. Which is why no action is without consequence and effect – a fact which we humans would do well to remember…

Jacqui Ikin & The Cross Country Team


What Termites Can Teach Engineers


How the thermal environment shapes the structure of termite mounds


Her Majesty, The Termite Queen

Termite World | Life In The Undergrowth | BBC

Amazing World of a Termite Mound | Wonders of Life w/ Prof Brian Cox | BBC Earth

Termites – The Inner Sanctum – Go Wild

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