Studies show a strong link between climate change and insect feeding patterns 58 million years ago.

Paleobiologists from the National Museum of Natural History in Washington studied fossil evidence of insect damage to plants from the cool Paleocene, and warmer Eocene epochs.

Clear link

Their findings, reported in Science magazine, show that as the temperature rose by an estimated eight degrees, so did the insect population and its appetite.

Peter Wilf and Conrad Labandeira identified 41 specific types of damage caused by insects. Leaves from the warmer period show more bite marks by a greater variety of insects.

The fossils came from southern Wyoming in the USA. They include members of the birch family, and the alder, both of which suffer heavy insect damage.

Increase in greenhouse gas

Insect activity linked to global warming

It is thought that the rise in temperature between the two epochs was caused by a steady increase in the amount of carbon dioxide in the atmosphere, although it is not clear what caused the increase.

"This study may not be able to directly predict future changes, but it goes a long way to explaining how climate can lead to different evolutionary histories," says Phyllis Coley, a biologist at the University of Utah.

The UK Government has announced increased insect activity is among a number of indicators to be used to monitor climate change.