Locusts' hairy legs triggered Biblical plague

Hairy legs led to one of the seven plagues of Egypt described in the Bible, scientists have discovered.

Hairy legs led to one of the seven plagues of Egypt described in the Bible, scientists have discovered.

A study of the same species of desert locust that had a starring role in one of the great Old Testament epics has revealed that touching the hairs on the back of the insect's leg turns it from a shy, retiring creature into a crowd-loving hooligan.

The Jekyll-and-Hyde transformation of the locust from its solitary to its gregarious form is well documented but scientists have until now been at a loss to explain precisely how it comes about.

When locusts are solitary they rarely cause any problems and actively avoid one another's company. However, when they are forced together in overcrowded conditions, their mood changes to a bolder, hungrier form with a tendency to form huge swarms.

Zoologists at Oxford University found that it is the frequent touching of the hindlegs during overcrowding that causes the transformation.

The findings have important implications for locust control which currently costs international agencies about $350m (£250m) a year in the form of monitoring for swarms and eradicating them before they can damage crops.

Stephen Simpson, who led the team from the University Museum of Natural History, said that understanding what causes the transition could be the key to finding new ways of tackling the pest in Africa.

"If you can understand this Jekyll-and-Hyde transformation you've got new targets to aim at for control," Dr Simpson said.

The study, which is published in the current issue of the journal Proceedings of the National Academy of Sciences, failed to find any other part of the locust's anatomy which could trigger the change.

"A switch from solitarious to gregarious behaviour occurred when the outer face of the hind femur had been stimulated, but mechanical stimulation of 10 other body regions did not result in significant change," the study found.