It is exerted when the caterpillar is harassed by a predator, and has a pungent odor which drives the predator away. In some species with eyespots, the osmeterium completes the illusion of snake mimicry by resembling the snake's forked tongue.

What is the function of Osmeterium?

The osmeterial organ remains inside the body in the thoracic region in an inverted position and is everted when the larva is disturbed in any way emitting a foul, disagreeable odor which serves to repel ants, small spiders and mantids.

Is Osmeterium poisonous?

confirmed that many components of osmeterial secretions from a variety of papilionid species are toxic and/or repellent to ants. To whom correspondence may be addressed. the chemical composition of osmeterial secretions varies ontoge- netically.