A high-rise home for 500,000 ants

Have pity for the poor, hard-working northern wood ant. It commits its life to lugging every available piece of forest detritus to its nest, only to find Britain's changing habitats are removing its raw materials and threatening its existence.

But ants in woods at Holystone, Northumberland, have reached new heights. Foresters looking after the 375 acres have found what may be Britain's largest anthill, 5ft 6ins (167cm) tall and housing 500,000 insects. What they call the "ant equivalent of the Empire State Building" has been built of spruce and pine needles and will have taken years.

Intensive afforestation and felling and urban developments have all contributed to the decline of the distinctive red and black wood ant (Formica lugubris). Nests elsewhere in Britain, mainly in the south, do not usually exceed two feet. Steve Morris, who oversees 30 woods in the Rothbury area, was astonished. "I couldn't believe its sheer scale," he said. "Wood ants are only a centimetre long and to build such a nest must have taken millions of ant hours and years of toil."

In most ant societies the insects have assigned roles at birth, such as foraging, digging, soldiering and looking after eggs and larvae. The nest centres on a queen, which lays up to 10,000 eggs a day. Workers maintain the nest, which has a dome like a thatched roof to shed water. The south side of the nest is flatter to present a greater surface area to the sun.

Conservationists say worker ants will "sunbathe" then go into the nest to release excess heat and keep eggs warm.