Tiny Architects

At sunset they look like squat people dotted across the plain. Here, 450 km below Karratha, the invisible population of the bush busies itself in mounds rising a meter or so above the spinifex scrub. Three hundred of the world's 3,000 termite species live in Australia. Most are rarely seen, but their monuments are everywhere on display.

Heading north, the structures seem to grow taller, until they turn into massive domes and spires. The largest mounds hold upward of a million insects working in blind harmony. Mounds can reach 7 m high and 12 m around the...