Invasion of the poisonous ladybird that is putting native species at risk... and bites

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Invasion of the poisonous ladybird that is putting native species at risk... and bites

 

By David Derbyshire

Last updated at 9:34 AM on 30th June 2009

 

 

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'Threat': The harlequin ladybird

 

The harlequin ladybird - an aggressive, toxic invader that has colonised Britain in just four years - is threatening more than 1,000 native species, scientists say.

Since it arrived in the South of England in 2005, the bug has spread at an incredible rate and is now found everywhere from Essex to Orkney.

This year, an estimated one billion will be munching through gardens, devouring the eggs of other ladybirds, butterflies and lacewings and spraying homes with toxic yellow chemicals.

The rise of the harlequin - which was introduced from Continental Europe as an 'environmentally friendly' pest controller - has stunned experts who say it is the fastest insect invasion in living memory.

Now a new study claims that the fast-breeding ladybirds are putting hundreds of native British insects, parasites and fungi at risk.

Although the harlequin is unlikely to drive native ladybirds to extinction, the invader may become so dominant it is the only ladybird people see.

The harlequin is a voracious predator. It eats almost every kind of aphid and will prey on the larvae of other ladybirds, caterpillars and lacewings.

Once it moves into a neighbourhood, it devours most of the food, leaving little for other insects to live on. It is at the top of its food chain - and has few natural predators in the UK.

Dr Helen Roy of the Centre for Ecology and Hydrology said native insects were likely to suffer 'severe declines' as harlequin numbers grew.

'We believe that the negative impacts of the harlequin on Britain will be far reaching and disruptive, with the potential to affect over 1,000 of our native species," she said.

'It's a big and voracious predator, it will eat lots of different insects, soft fruit and all kinds of things. Its reproductive capacity is also immense.'

Some of the losers are insects that the harlequin eats. Others are parasites that feed off the harlequin's chosen food. And some are creatures out-competed by the invasive bug.

Harlequins are far bigger and more aggressive than most native ladybirds such as the two spot and seven spot. They will breed several times a year. Although their appearance varies hugely, they are all large - around 7mm.

'My biggest concern is for the two-spot butterfly, a small bright ladybird,' said Dr Roy.

 

'A few years ago it was commonly seen, but we are struggling to see them now. It lives in the same habitat as the harlequin but it doesn't have its size or voracious appetite.'

The seven spot ladybird is also at risk, she said.

Researchers are not encouraging people to kill harlequins as it would make no difference to the overall numbers and they may accidentally kill native species.

Unlike native British ladybirds, the harlequin - Harmonia axyridis - produces a noxious, foul- smelling chemical that can stain furniture and walls. They can also bite people, triggering an allergic reaction.

In the autumn they swarm over walls, in homes and in attics looking for a safe place to spend the winter.

Harlequins are known in America as Halloween ladybirds because they appear in homes at the end of October. They are also called the multicoloured Asian.

They were introduced to the US from Asia 25 years ago as a form of pest control. They spread to Europe and reached the UK four years ago.

Although they prefer aphids, they will try anything they come across when hungry - and have even been seen eating the caterpillar of a brimstone butterfly.

Scientists are presenting the latest research on the harlequin at the Royal Society Summer Exhibition this week.