Swallowtails, when disturbed, often flash their osmetaria or scent horns. These organs simpy emit a foul odor that acts as a repellent but can also be visually intimidating. Osmetaria are harmless.

Thanks rhizo. I am not an entomologist. Thanks for the word: osmeterium . Here is what wickpedia wrote: Normally hidden, this forked structure can be everted when the caterpillar is threatened, and used to emit a foul-smelling secretion containing terpenes. I was referring to the secretion. I will review my videos. I do not believe I ever succeeded in capturing the actual event on tape.

I looked up terpenes on wikpedia: Terpenes (pronounced /ËtÉrpiËn/ TUR-peen) are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers,[1] though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. I am still fuzzy on wether it is an aromatic love potion or a solvent ( like turpentine.