from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An eversible glandular sac on the first thoracic segment of many caterpillars that secretes an unpleasant-smelling substance to ward off predators.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. One of a pair of scent organs in the larvae of certain swallowtail butterflies.

from The Century Dictionary and Cyclopedia

  • n. In entomology, any organ devoted to the production of a scent or odor; specifically, a forked process found on the first segment behind the head of certain butterfly-larvæ.


New Latin osmētērium, from Greek osmē, smell.
(American Heritage® Dictionary of the English Language, Fourth Edition)
New Latin, from Ancient Greek ὀσμή (osmē, "smell"), ὀσμητός (osmētos, "smelled"). (Wiktionary)


  • Not only do the earliest books that I can find spell it "osmeterium", but the Greek root is "osme".}

    Explanation of Terms Used in Entomology

  • The Black Swallowtail Caterpillar has an orange “forked gland”, called the osmeterium.

    Whoa Nellie!* « Fairegarden

  • As with other swallowtails, these caterpillars 'posses a bright reddish orange, y-shaped gland called an osmeterium, which contains a mixture of highly noxious chemicals that smell like rancid butter.

    Museum Blogs

  • I didn’t know about the osmeterium — kinda freaky!

    Whoa Nellie!* « Fairegarden

  • When in danger the osmeterium, which looks like a snake’s tongue, everts and releases a foul smell to repel predators.

    Whoa Nellie!* « Fairegarden


Log in or sign up to get involved in the conversation. It's quick and easy.