The Secret Weapon of the Harlequin Ladybird

Meet the harlequin ladybird, a global pest controller with a hidden talent. This beetle, originally from East Asia, has become an invasive species in Europe and North America. Scientists found that when harlequin ladybirds eat the eggs of seven-spotted ladybirds, they stay healthy. But the seven-spotted ladybirds can't do the same unless they're given penicillin. Why? It turns out there's a tiny ally inside the harlequin ladybird eggs – a new kind of bacteria called Serratia harmoniae.

This bacteria is much more dangerous to the seven-spotted ladybirds. The harlequin ladybirds have a secret weapon called harmonine that helps them fight off this bacteria better. When scientists stopped the ladybirds from making harmonine, they got sicker. But giving them penicillin made them better again. So, the harlequin ladybird has a special advantage over other ladybirds, thanks to its bacteria friend and its own secret weapon.

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