Swallowtail caterpillars have a bright orange/red fleshy organ called an osmetrium. It looks like a serpent tongue that they stick out when they are disturbed to scare off predators. Osmetria give off a bad smell when stuck out - from two chemicals released from it. I came across this one on an Satsuma orange tree in my backyard garden. When I touched the branch - look what happened!
