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Giant Swallowtail Caterpillar Osmetria – Red Forked Tongue?

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Swallowtail caterpillars have an 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 Satuma orange tree in my backyard garden. When I touched the branch – look what happened!

Swallowtail Organ OsmetriaSwallowtail Organ Osmetria
Swallowtail Organ Osmetria

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  4. Lisa says

    That is so awesome!!!! Poor thing looks like Adams Familys’ Cousin It of the caterpillar world. LOL

  5. Linda Rippert says

    Great photos. The public needs to know about this phenomenon of swallowtail caterpillars and be prepared to look for it in their home gardens. The Ft. Bend Co. Master Gardeners have an Entomology committee that actively helps educate gardeners about the critters in their gardens and studies hard to learn more about Nature’s insects, etc.

  6. Nancy Jarmin says

    Beautiful photos. I always learn something from your posts. Thank you for all you do to help gardeners

  7. V. Hale says

    Thanks for the beautiful photos! I plant dill just for the caterpillars which love that plant and have noticed the same reaction/smell when transferring the dill caterpillars to another plant. They can be quite feisty – and, if I were a predator, I’d leave them alone as well since the smell is quite distinctive!

  8. Melissa Evenson says

    I think I have the same critters eating up my young grapefruit tree. Last year they attacked my young lime tree. I won’t disturb them because they will be butterflies one day, but it is annoying to loose all those leaves! I blogged about it as well. Thanks for sharing.

  9. RI says

    I have 2 and they have been eating my orange tree leaves. Not very pleasant odor… Nothing seems to kill them, now what do we do?

    • Jackie D'Elia says

      Why would you want to kill them? Rarely do they do enough damage to affect the health of the tree. The butterflies they do become are beautiful.

  11. ESP says

    What a fantastic sequence of photos Jackie. Winston Churchill would be proud 🙂
    These are great caterpillars to find.

  13. Charlie says

    Your photos are absolutely amazing. I am really intrigued by butterfly’s and have been shaping my garden over the past three years so I really appreciated your post.