Urticating Hairs

While “hairs” technically are only found on mammals, sharpened venomous spines, setae or bristles serve as a defense mechanism for certain plants, tarantulas, marine invertebrates and caterpillars. Like tiny syringes, these finely sharpened spines are hollow and loaded with an acrid fluid irritant. Displaying these spines, along with aposematic coloration, gives warning to any who dare approach with ill intent.