By Richard Black
Environment correspondent, BBC News
A giant ant growing over 5cm (2in) long crossed the Arctic during hot periods in the Earth's history, scientists say, using land bridges between continents.
The ant, named Titanomyrma lubei, lived about 50 million years ago and is one of the largest ant species ever found.
Fossils were unearthed in ancient lake sediments in Wyoming, US.
Writing in the Royal Society journal Proceedings B, a Canadian-US team shows that giant ants, now and then, almost always live in hot climates.
The new species appears very similar to fossils found in Germany and in the Isle of Wight in southern England dating from the same period.
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http://www.bbc.co.uk/news/science-environment-13269302