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Endurance of the beetles

21 December 2007

What accounts for 25% of all living things on Earth? Beetles. They are some of the most successful creatures to have lived and new research published in the journal Science today suggests that they may also be the most enduring.

Scientists at the Natural History Museum and Imperial College have discovered that most modern-day beetle groups first appeared during the Jurassic period at the time when the major groups of dinosaurs appeared too.

Six-legged survivors

These beetle groups out-lived the dinosaurs and diversified into the 350,000 species we see today. There are probably several million more species still to be discovered.

'The large number of beetle species existing today could very well be a direct result of this early evolution of many modern-day lineages,' says Professor Alfried Vogler, lead scientist on the study. 'There has been a very high rate of survival and continuous diversification of many lineages since then.'

Evolutionary study

The team studied the DNA of 1,880 species of beetles and was able to produce an evolutionary family tree. This helped them look at the relationship between different species and identify common ancestors.

Fossil data was then used to obtain key dates in evolution history. This is the most extensive beetle evolutionary study carried out to date.

Successful adaptors

Beetles are extremely good at adapting to new ecological environments, changing their life styles and feeding habits when acquiring new surroundings. For many years scientists have debated why beetles are such successful survivors.

'Unlike the dinosaurs, which dwindled to extinction, beetles survived because of their ecological diversity and adaptability," Vogler says.

One theory for the beetles' success has been the fact that they are herbivores (eat plants). It is thought that beetles diversified around the time flowering plants diversified in the Cretaceous era wihch provided a new resource for the beetles. The flowering plants first originated around 140 million years ago and this new research shows beetles had already diversified long before this time.

Understanding evolution

Understanding the evolution of beetles is an important part of understanding the natural world, such as the evolution of other life forms and how diversity evolves.

'With beetles forming such a large proportion of all known species, learning about their relationships and evolution gives us important new insights into the origin of biodiversity and how beetles have triumphed over the course of nearly 300 million years,' Vogler concludes.

Briliant beetle facts
  • One in four living things are beetles.
  • There are more than 300,000 beetle species, compared with only about 5,800 mammal species.
  • The 'feather-winged' beetles of the family Ptiliidae are amongst the world's smallest insects. Measuring as little as 0.21mm they are even smaller than some species of protozoa (single-celled animals) and much smaller than a pinhead.
  • The heaviest and bulkiest of all insects are the Megasoma beetles of South America. The heaviest species is Megasoma actaeon, whose fully grown larva can weigh in at over 200g,  heavier than an ipod.
  • Rhinoceros beetles are proportionally some of the strongest animals in the world. Some can lift 850 times their own weight - equivalent to an average adult (70kg) lifting seven double-decker buses.
  • The world's longest beetles are the Hercules beetles found in Central and South America, measuring up to 19cm long - over half of which is their long horns.
  • The longest beetle without horns is the titan beetle Titanus giganteus from the Amazon region, which still up to 16.7cm long.
  • Jewel beetles (family Buprestidae) can survive for 30 years or more.
  • The world's fastest running insect is the Australian tiger beetle (Cicindela hudsoni), which can run 9km/h (5½ mph). It is a voracious predator chasing down its prey at high speed.
  • The bombardier beetle can shoot boiling hot puffs of irritating gas from its anus, which the beetle can aim with remarkable accuracy and turn on and off 500 times a second.
  • Larvae of large weevils, June beetles, or long-horn beetles are eaten by native peoples in South America, Australia, and Asia.
  • The highest g-force endured by any insect is an average of 400g by the click beetle (Athous haemorrhoidalis).
  • If the click beetle finds itself on its back it can right itself by using tiny peg on the underside of its body to build up tension in its body muscles. Their name comes from the click as the peg slips,  propelling the beetle up to 30cm into the air.
  • Early Egyptians perceived the Earth as a ball of dung pushed through the universe by a dung beetle, and used this beetle as the image for their sun god, Khepera.

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