osmeterium

Definition

A glandular organ found in the larvae of swallowtail butterflies (Papilionidae) that emits a foul-smelling chemical to deter predators.

Etymology

From Greek 'osmē', meaning 'smell', and '-terion', a suffix used to name various small biological structures.

Example

When threatened, the caterpillar of the Eastern Tiger Swallowtail extends its osmeterium to release a strong, unpleasant odor.

Synonyms

• Defensive gland

Related Terms

• Caterpillar
• Swallowtails
• Chemical defense
• Larvae

Usage Notes

The osmeterium is typically hidden when not in use and can be everted in response to threats. It is most effective against small predators like ants and spiders.