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You may not have heard of the Harlequin Ladybird. I hadn’t until one of our sharp-eyed youngsters, Celia, spotted some clusters of ladybirds inside the windows of the tower stairs. By coincidence, a few days later, I read an article about the invasion of an alien ladybird, so I set about identifying the ones in the tower, which were indeed Harlequins. This might be one bit of bio-diversity that we don’t want to encourage.
Harmonia axyridis (to give it its scientific name) is a native of eastern Asia. It occurs naturally from Siberia, through Russia to Japan, and south to Mongolia, China, and the Himalayas. Other countries have introduced it as a biological control agent, including North America in 1988, since when it has become the most widespread ladybird species there. Nearer to home, it has become established in France, Germany, Belgium and Holland. In summer 2004, it arrived in England, probably by flying the Channel as well as hitching a lift with imported flowers, and it has since spread across much of the country.
The Harlequin thrives in diverse habitats and eats a wide range of food, so it can easily out-compete our native ladybirds. As well as small insects, eggs and larvae, it eats pollen, nectar, honeydew and the juice of fruit. When food is short it eats the other ladybirds as well. Bio-diversity isn't the only concern though. Harlequins can damage late summer fruit by feeding on its juice. Wineries are finding many of them in the grape harvest, where they are difficult to separate from the grapes before pressing, and where their defensive chemicals taint the wine.
Harlequins like to gather in buildings during autumn and winter, but people find them a nuisance and don't wish to share their homes with thousands of them. Their defence mechanism can make them unpleasant to deal with. They exude a yellow fluid (called reflex blood) which has an unpleasant acrid smell, and causes stains. I picked one up on a piece of paper, and the tiny spec it left behind did indeed smell noticeably. When woken from dormancy by central heating, if there is no food around they may also bite people, which can be unpleasant.
There is a website dedicated to the Harlequin: www.harlequin-survey.org It includes a pictorial guide showing how to distinguish then from our native ladybirds (at first sight, they look similar, but the differences are clear when you look in detail). There is also a form for you to report any sightings, and help complete the picture of their spread – we reported ours. We had relatively few of them – clusters of a couple of dozen in three separate windows, most of which seem to have died off. Let’s hope they don’t arrive in force next year.
John Harrison ( February 2008 )
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