[Photo] Hercules beetle. One in four living things are beetles.

Most modern day groups of beetles have been around since the dinosaurs.

It was thought that today's beetle lineages evolved alongside the arrival of flowering plants, some 140 million years ago.

However, a report in the journal Science has pre-dated their appearance by 110 million years, back to the Jurassic period.

Very soon after beetles originated, they evolved into the lines that persist today, researchers say.

Co-author Dr Johannes Bergsten from Imperial College London, UK, told BBC News: "We found that five small families, that are the oldest lineages to the rest of the major beetle group, go back over 250 million years."

There are more than 300,000 species of beetles on Earth, accounting for a quarter of all living things.

The reason for this large number of beetle species has been debated for many years and never resolved.

Co-evolution with plants?

Prior to this study, the diversification of beetles was attributed to the arrival of flowering plants, in the Cretaceous Period (145-65 million years ago).

Dr Bergsten said: "Each species of plant could be a separate niche for a species of beetle. So the more plants there are, the more niches there are for different species of beetles."

However, the study found that more than 100 families of today's beetles were already present before that.

What causes this high speciation rates remains unknown and continues to puzzle researchers. "We don't have the answer to that," Dr Bergsten says.

Beetles have displayed an exceptional ability to seize new habitats and have developed novel ways of feeding to exploit different vegetation.

Lead author Professor Volger added: "Unlike the dinosaurs which dwindled to extinction, beetles survived because of their ecological diversity and adaptability."

Key innovation

This ability is mainly attributed to their key innovation of a hard casing. "[Beetles] were able to exploit very narrow niches, live under rock and live under bark, and still protect their hind membranous wings so they could disperse and exploit habitats," Dr Bergsten explained.

The scientific team believes that understanding the evolution of beetles is an important part of understanding the natural world.

"If we try to understand how beetles diversified we have understood at least one fourth of how the biodiversity of the world came about," Dr Bergsten said.

"Beetles have a good track record of being around for some 300 million years, and are still prosperous. I think they will be around for a long time to come."