Cinnabar moth Tyria jacobaeae

Bold red patches against jet-black wings make this one of nature's most striking warning advertisements—a visual shout of "Don't eat me, I'm poisonous!" It acquires toxicity from ragwort plants, which its caterpillars munch relentlessly, accumulating poisons that deter predators. Named after the vivid red mineral cinnabar, this Eurasian native is unmistakable once seen.

Here's what makes it remarkable: it's been deliberately introduced to New Zealand, Australia, and North America as a biological control agent against invasive ragwort. The caterpillars are ragwort specialists, and farmers hoped they'd control this agricultural weed. In a rare twist, what's usually a pest becomes a gardener's ally—though with mixed success in its new homes.