SVR Murthy
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Termites are organized social insects that live in large colonies. Termites are almost everywhere beneath us, we can’t see them because the termite nest might be as deep as 10 feet beneath us. A single colony may house 2 million termites that’s why it’s been said that the total weight of all termites in the world is heavier than the total weight of all humans.

                          

Termite mounds are built from compacted soil and contain a network of tunnels that transport gases from the nest to the mound surface, where they diffuse through many tiny pores that also allow outside gasses to enter the mound. Because the individual pores are so small, however, the mound resists large-scale pressure-driven airflow such as that induced by wind—the ventilation must instead be driven by some other factor.

To determine what this factor could be, the researchers studied Odontotermes obesus, a species of mound-building termite found in southern India. They measured airflow speed and direction inside both living and dead mounds, as well as carbon dioxide concentration. Carbon dioxide levels rose during the day and then, as the temperatures dropped at night, fell sharply. Air velocity also fluctuated in accordance with these daily temperature cycles.

That understanding of termite mound function has already inspired human architecture -- including a building in Zimbabwe designed without air conditioning that instead uses wind energy and heat-storing materials to maintain a moderate temperature. The only problem with these sorts of termite-inspired designs, Turner said, is that his studies show that the mounds actually don’t work that way.

Deploying temperature and humidity gauges, and armed with tracer gases, Turner found that a termite mound does not regulate interior temperature. The temperature inside the mound was not appreciably different from that of the surrounding ground, rising during some parts of the year and then falling. In addition, he found that the air in the nest didn’t really circulate. Instead, it was stable, with cooler air in the nest low in the mound and hotter air in the mound’s upper portions and chimney.

The same fluctuation wasn’t found with humidity, which was maintained at roughly 80 percent year-round. But it isn’t the mound or its design that does that job, Turner said. Instead, termites actively move water within and out of the mound as they transport water-soaked earth. In addition, the symbiotic fungi that live in the mound with the termites also help to regulate humidity. The fungi, which help the termites digest tough cellulose in the plant material the insects bring into the nest, form complex, folded bodies that absorb excess humidity during wet months and release water during dry months, Turner said. This helps to maintain a stable humidity, dry enough to keep moisture-loving fungal competitors at bay

the tunnels work as an air exchange system. The smaller tunnels on the mound’s surface, used by workers to move in and out of the mound, also serve to mute the gusty, turbulent air outside the mound. Those high-energy gusty breezes are blocked in the surface tunnels, allowing more gentle air movements to penetrate the mound in a pulsing, in-and-out process akin to a breathing human lung. Through this process, fresh air is exchanged into the deepest part of the mound, “sloshing” in and out in a tidal movement that refreshes the mound’s air.