Scientists have pinpointed why insect life is so varied - because plant-eating bugs stick to their own tiny neighbourhoods to reduce the chances of being eaten.

Insects have adapted to live in particular circumstances - such as the leaf or root of a plant at a particular time of year - to limit their number of potential predators. Researchers at the University of Edinburgh say this helps explain why the creatures have diversified to account for one-third of all animal species.

The study has found that bugs which live in similar circumstances are often attacked by the same predatory insects.

Different parts of a single tree, at various times of year, can feature struggles between many plant-eating insects and their enemies. This helps to explain why, for example, as many as 800 species of insects may be found in one English oak tree.

The study focused on gallwasps - tiny wasps that live in oak trees, in homes known as galls, and showed that their galls provide defence against their enemies. Each gallwasp lives in a particular type of structure, in a specific place on a distinct type of oak at a certain time of year, and the circumstances influence which predators are able to attack.

The gallwasps' enemies have evolved countermeasures to some gall defences, but not all - the insects are engaged in an evolutionary arms race that has lasted for at least 40 million years.

The research was carried out by the University of Edinburgh, University of Reading and the Centre for Ecology and Hydrology, together with researchers in Hungary. The study was funded by the Natural Environment Research Council and published in PLoS Biology.

Dr Graham Stone, of the University of Edinburgh's School of Biological Sciences, said:

"The diversity of insects on Earth is staggering, and one of the mysteries has been how so many species can survive essentially in the same place. Now we understand more about how these different species can coexist on a single tree. Our findings also shed light on how insects can use the plants on which they live for protection against their enemies."

For more information please contact:

Dr Graham Stone, School of Biological Sciences, tel 0131 650 7194; email Graham.Stone@ed.ac.uk

Catriona Kelly, Press and PR Office, tel 0131 651 4401: email Catriona.Kelly@ed.ac.uk