Attack of the Killer Ladybirds

16 July 2009

Caption:  Harlequin ladybird eating a beneficial lacewing

Last April my office window filled up with dozens of ladybirds. I didn't know what to do, so I called up a ladybird site I found on the internet. Describing the ladybirds to them I was told that these were the foreign, killer Harlequin ladybirds.  This was my first introduction to these pests.

They come from Asia.  They are voracious, even eating our own ladybirds.  This year they are invading again, as the hot weather is favourable for them. The Harlequin has a particularly recognisible W shape on the front of its wing-case.

They first arrived in this country in 2004 and are an environmental pest because, although they eat lots of aphids, they also eat all sorts of other species, both beneficial and harmful. Originally introduced to Europe to control pests, they have migrated to the UK, probably in bunches of flowers. Unfortunately, harlequins will also eat non-pest and beneficial insects, including the larvae of other ladybirds and the eggs and larva of butterflies and moths. Britain's 45 species of native ladybird and these other insects play a key role in our ecosystem, but the harlequin has the potential to jeopardise many of them.

Dr Helen Roy of the Centre for Ecology & Hydrology is leading the project to monitor the harlequin's spread and impact on native species. She said the negative impact on Britain could be far reaching and disruptive, with the potential to affect over 1000 of our native species. "In the United States, where the harlequin arrived over 20 years ago, it has been associated with severe declines in native species, " Dr Roy explained.

Caption:  Harlequin Ladybrid egg laying

"Invasive alien species are one of the greatest threats to global biodiversity," says co-investigator Dr Remy Ware, from the University of Cambridge. "Using data from the Harlequin and UK Ladybird Surveys, we have a unique opportunity to study the early establishment, spread and adaptation of an invasive species."
The research team are now exploring how the few native enemies of the harlequin that do exist could be used to control the invasion. One idea is to use a sexually transmitted mite, which makes some ladybirds infertile. If the transmission of the mites could be encouraged, the harlequin population could become greatly reduced. Other possible control options involve fungal disease, male-killing bacteria, a parasitic wasp and parasitic flies.
The scientists will be on hand at a Royal Society exhibition, to talk visitors through their research. Visitors can learn how to distinguish harlequins from native species, get up close and personal with harlequins under the microscope, and find out more about how scientists are trying to control the invasion.

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