This Stick Insect Has a Peppermint-Scented Secret Weapon

Ah, to be a stick in this world. A stick that can dance in the gentle breeze. A stick that, unfortunately for it, tastes better than your average stick. A stick that can, surprise, fight back with a self-defense solution. It's a peppermint stick named for the peppermint-scented spray that it aims and fires forward or backward from glands just behind its head. Though mint may remind us of a relaxing cup of herbal tea, to predators it's a noxious smell and irritating chemical. If an animal gets hit in the eyes, mouth, or antennae, it'll burn or disorient them. This defense is so critical to their survival that newly hatched peppermint sticks, called nymphs, are able to spray immediately, before they even take their first bite of food. That means their mothers transfer the defensive chemicals into each egg. Like most stick insects, its first line of defense is its very specific disguise. Wild peppermint stick insects live, feed, and breed on pandanus plants. The plants and insects have evolved together over millions of years. More than just food, the plants give them what they need to make actinidine, the active ingredient in their defensive spray. You'll find them in the Daintree Rainforest in northeastern Australia, the oldest tropical rainforest in the world. A living Jurassic Park, it's more than twice as old as the Amazon. Surrounding this clumsy vegetarian are ruthless predators. And hiding will only get you so far. These tiny green tree ants can actually be a huge threat. They're voracious, constantly foraging for plants and animals, living or dead. And if they come upon a peppermint stick, it could be fatal. If our friend does run into hungry ants, first it tries a few evasive maneuvers. Of course, when things get drastic, it's time to fight. The ants are tenacious. These attackers can spray too, shooting a tiny jet of toxic formic acid. Enough of that can injure or immobilize the stick insect. It's all-out chemical warfare. The stick's counterattack is not a magic bullet, but a direct hit of the pepperminty brew irritates the ants, overloading their sophisticated sense of smell. This peppermint stick is lucky to get away with just a battle scar. Because it's a juvenile, that leg can actually regrow when it molts. The battles between peppermint stick and ant will rage on. They're both an important part of the delicate balance of the food web in this rainforest. Lesson learned. Being a stick is not so easy breezy. Gotta have your pepper spray. Peppermint spray, that is. If you like this video, please consider supporting KQED, the PBS station that produces Deep Look. Donations from viewers like you allow us to continue making our award-winning series. Click the link on screen or in the description below.