Articles

Termite mounds: cities in miniature

By Shaun Doyle 4-2011

Termites can be real pests. They chew through the wood in our homes, and can eat a home inside out, making it completely unlivable. The irony is that termites can build not just houses, but veritable cities of their own. These ‘cities’ house, feed and protect them with great efficiency, and with very little wastage. Termite mounds can be as high as 9 m (30 feet). If this were scaled up to human terms, that would be like building a structure 2 km (1 ¼ miles) high! And not just any structure either: it would involve a nursery, farms, and a massive ventilation network to keep the building air-conditioned.

Temperature control

Termite mounds can be found in climates with severe temperature extremes, where daily temperature variation can be up to 30°C (54°F 1). Termites have a number of ways to deal with such extreme temperature differences.

In dry climates, termites follow the same principle as the people of Coober Pedy in outback Australia, who mostly live underground. The termites bury their nest beneath the mound, well below ground level. Despite the heat fluctuations on the surface, the soil acts as an enormous heat sink. Due to this large ‘thermal mass’ of the surrounding soil, the temperature barely changes throughout the day.

In addition, the spires of their mounds are constructed to point towards the average position of the sun at midday. This minimizes the area exposed to the sun’s rays in the hottest part of the day, which helps to keep daytime mound temperatures constant.

Living underground is, however, not an option for some termites, such as the ‘magnetic termites’ of northern Australia. They live in wetter climates, so an underground nest would be flooded in the wet season. 2 To avoid this, they live inside their mounds above the ground surface. But this brings the colony much closer to daytime temperature extremes, especially in the dry season.

So these termites orient the broad faces of their mounds east-west to help control nest temperature. 3 The colony also stays near the eastern face of the mound during the day because it affords the most constant temperature.

Many termite species have fungal ‘farms’ that supply most of the colony’s food. Workers forage for bark and bring it back to the nest, and the fungi live off the bark and make it more digestible and nutritious for the termites. 4 For dry-climate termites that live underground, this presents another problem. How can they breathe underground, especially as the colony grows larger?

Lungs for the colony

Research has shown that termite mounds behave like lungs, enabling the colony to breathe. 5 The mound is designed to capture small air currents and eddies in gusts of wind that vibrate with a low frequency, while air vibrating at higher frequencies is not permitted to enter the mound. 6 This low-frequency air is ‘pushed’ into the mound and down into the nest by the force of the wind hitting the mound. Likewise, the stale air is sucked up and out of the mound by the pressure difference caused by the directional flow of wind against the mound. This combines with upward flow of air from the nest caused by insect and fungal activity to create a very complicated flow pattern somewhat like a human lung, allowing air to be exchanged with the outside environment.

Moisture control

Termite ‘cities’ found in arid climates remain moist in the underground nest all year round. 7 The insects need a moist atmosphere not only for their own survival, but also for their fungal ‘farms’. Termites construct long tunnels, often tens of metres long, down to the water table to access water. During the wet season, the termites regulate the moisture of both the mound and the underground nest (by moving moisture-laden batches of soil around). In the dry season, it would be much harder to keep both the nest and the mound at optimum moisture, so they concern themselves only with the nest. Mounds built in the shade, where there is less evaporation, are much smaller than those in the open, because there is less need for termites to transfer moist soil pellets from below and add them to the surface of the mound to keep it and the nest moist. So the size of the mound shows the degree of moisture regulation that has taken place.

Group intelligence

The question is: how do termites manage to build such masterpieces? Humans have not yet built anything that exceeds the efficiency of termite mounds, yet termites are not intelligent. They provide examples of self-organization. 8 This is where a complex structure or pattern arises in a system without any central authority, plan or blueprint organizing it. A globally coherent pattern emerges via the local actions and interactions of many individual units (e.g. insects) combined, yet with no overarching coordination between the units.

A prime example is how termites rebuild or repair the mound when it has been removed or damaged. 9

It doesn’t take long for the colony to realize something is wrong with this delicate balance of temperature, moisture and airflow. Within five minutes of damage being done, termites are at the scene investigating what happened.

Within an hour, they are replacing soil at the damaged site. The termites instinctively lay soil pellets laced with chemicals called pheromones (‘smell hormones’) which attract other termites to lay more (pheromone-laced) pellets, in an effect which snowballs. The overall ‘objective’ (and the eventual outcome in most cases) is to stop the turbulent air flow caused by the breach. A day or two of blockade building is usually enough to block off the damaged area.

But the unneeded blockades from such uncoordinated activity have themselves disrupted airflow. So for reasons not yet clear, the termites then move into a remodelling phase, where soil is progressively moved from the blocked tunnels to the outside of the mound. The end result of all this unplanned activity is that the shape of the mound is restored, making the mound an effective ‘lung’ for the colony again. They can even reconstruct an entire mound ‘from scratch’ within 3 months!

All this is done without forethought or language—no individual insect is ‘purposely’ working for the good of the whole. But it needs the right ‘algorithm’ so that this sort of complex result can emerge. This requires the right programming within each insect’s DNA, and programs require intelligence to write them in the first place. 10

God’s wise builders

Termites, like ants, have no rulers. 11 Yet they can build such amazing structures which they use to help them breathe, keep warm and moist and to keep their ‘farms’ productive. The Bible long ago recognized the amazing diligence of ants. Its words apply just as much to termites, their fellow social insects: “Go to the ant... (Proverbs 6:6–8 ESV). Termites, and the masterpieces they build, are a testimony to a wise Creator. He gave them the programming required so that, though having no intelligence themselves, they could ‘spontaneously’ produce such complex wonders.

References and notes

• 1. This temperature range is not to be confused with an actual temperature of 30°C, which is 86°F. (Zero on the Celsius scale is 32 on the Fahrenheit scale, hence 32+54=86)..
• 2. Schmidt, A.M. and Korb, J., The biological significance of Magnetic Termite mounds, The IUSSI 2006 Congress, Washington, DC, iussi.confex.com/iussi/2006/techprogram/P1435.HTM, accessed 30 September 2010..
• 3. Turner, J.S., Termite mounds as organs of extended physiology, www.esf.edu/efb/turner/termite/termhome.htm, accessed 23 August 2010..
• 4. Aanen, D.K., As you reap, so shall you sow: coupling of harvesting and inoculating stabilizes the mutualism between termites and fungi, Biology Letters2(2): 209–212, 22 June 2006..
• 5. Turner, J.S., On the mound of Macrotermes michaelseni as an organ of respiratory gas exchange, Physiological and Biochemical Zoology74(6):798–822, 2001..
• 6. Ball, P., For sustainable architecture, think bug, New Scientist2748:35–37, 20 February 2010..
• 7. Turner, J.S., Marais, E., Vinte, M., Mudengi, A. and Park, W.L., Termites, water and soils, Agricola16:40–45, 2006..
• 8. Theraulaz, G., Bonabeau, E. and Deneubourg, J.-L., The origin of nest complexity in social insects, Complexity3(6):15–25, 1998..
• 9. For the mound repair process, see Turner, J.S., Mound repair and mound structural homeostasis, www.esf.edu/efb/turner/termite/structural homeostasis.html, accessed 27 September 2010..
• 10. Many evolutionists, including Richard Dawkins, invoke examples of self-assembly to justify evolution. For refutation, see Sarfati, J., The Greatest Hoax on Earth? Ch. 5: Embryos and self-assembly, CBP, 2010..
• 11. The role of the ‘queen’ is largely reproductive; she exercises no oversight on the functions of the colony.

http://creation.com/termite-mounds