Giant swarms of cannibalistic Harlequin ladybirds riddled with an STI are invading British homes: this is a headline in the Mail Online this week. No wonder our relationship with our environment is deteriorating when the country’s most-read news outlet uses such inflammatory language to describe a natural phenomenon. Swarm, cannibalistic, riddled, sexually transmitted infection, invade: could they have squeezed any more knee-jerk melodrama into a single sentence?
Last year, harlequin ladybirds hibernated in thousands inside the noticeboard at the park’s entrance: not technically a swarm (swarms move) but certainly a lot. This behaviour seems to improve their chances of surviving the winter; it is one of the factors contributing to the rapid increase in their numbers since they arrived in this country in the summer of 2004.
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Harlequins don’t appear to be any more cannibalistic than any other species of ladybird. All those pretty red wing-cases with black spots hide predators. We may quote nursery rhymes at them (fly away home…) but the prey of all ladybirds includes the eggs and larvae not only of other species of ladybird but their own species as well.
The harlequins have brought with them a microsporidian parasite, which does no harm to the harlequin, but if it infects other ladybird species, such as the native seven-spot ladybird it invariably kills them. The culprit exists in the eggs and larvae of all harlequin ladybirds, but in a dormant and apparently harmless state. Native species, with no resistance to the parasite, are infected when they eat the eggs and larvae of the harlequins.
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The harlequins are colonisers and, like all colonisers, have carried diseases to which they are resistant, into populations that have no resistance at all. It works both ways though: harlequins have become infected by a local fungus common to our native two spot ladybird. The two spots transfer the fungus between themselves when they hibernate in groups or when they mate; nobody is sure how it was originally transmitted to the harlequins but it has spread among them in similar ways. It takes some real red-top journalism to turn that into riddled with an STI.
Harlequins are truly invasive, spreading faster than any other invasive species in our country, and we should be concerned – but not for tabloid misinformation constructed with dog-whistle weasel words into a crisis, but for our habit of moving alien species around the planet for our own purposes and with no regard for the consequences.
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Another invasive species here:
Southwick Country Park Nature Reserve 
intersting and informative reading. We have had a large number around and in our home too.
The hot summer hasn’t helped. The same thing happened after the summer of 1976 but then the ‘invasion’ was from France rather than Asia and the ladybirds weren’t harlequins; the newspapers reported it with the same breathless disregard for any scientific truth, though.
It’s worrying that they are using the same language as they use to stir up ant-immigrant feeling.