Solar-powered architecture
In the floodplains of Litchfield National Park, hundreds of grey, tombstone-like slabs rise from the grasslands. These are the work of the compass termite, Amitermes meridionalis, and they are a effective solution to thermal engineering. The mounds, which can reach heights of 4 meters and widths of 2.5 meters, are consistently oriented with their long axis pointing north-south. This precise alignment gives the termites their common name, "magnetic termites," but their compass is the sun, not the Earth's magnetic field.
The shape and orientation are critical for thermoregulation. The broad eastern and western faces of the mound catch the low-angled sun in the morning and evening, rapidly warming the structure after cool nights. During the intense heat of midday, the sun strikes only the thin top edge, minimizing heat absorption and preventing the colony from overheating. This architectural strategy is so effective that the interior of the mound maintains a relatively stable temperature and high humidity, essential for the termites' survival. Experiments have shown that rotating a mound 90 degrees, to an east-west orientation, causes internal temperatures to rise by as much as 7°C, to a lethal 42°C.
The mounds are built in low-lying grassy areas that flood during the rainy season. Building upward allows the colony to survive when the ground is waterlogged for weeks at a time. A single mound can stand for 50 to 100 years and house up to a million individual termites.
A self-contained city
Each mound is a complex and self-sufficient colony. It houses a queen and king, along with workers, soldiers, and reproductives. The outer walls are hard and durable, made from a mixture of soil, saliva, and feces. Inside, a network of tunnels and chambers connects nurseries and food stores, with walls the consistency of paper. The soldier termites, which defend the colony, are typically 4 to 6 millimeters long with curved mandibles.
The species Amitermes meridionalis feeds primarily on grass and other plant material gathered from the surrounding soil. This food is processed within the mound, sustaining the entire colony. The stable, humid interior created by the mound's architecture is important for this process and for raising young termites. The entire structure is a single thermoregulated organism, allowing the colony to thrive in an environment of extreme temperature fluctuations. The termites even adapt their building orientation based on local conditions; mounds in windier or more shaded locations may deviate slightly from a true north-south line to maintain the optimal internal temperature.