#osmeteria

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Pipevine swallowtail eggs and caterpillars in the yard.

Cochise County, Arizona, September 2024.

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Black swallowtail caterpillars revisited.  Cochise County, Arizona, September 2022.

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Pipevine swallowtail caterpillars revisited.  Cochise County, Arizona, September 2020.

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Like other swallowtail caterpillars, these pipevine swallowtail caterpillars have an interesting defense mechanism - hornlike organs behind their heads that are only visible when they feel threatened, as in the third photo.

These organs, called osmeteria, are covered with a sort of chemical repellent.  In this case the whole caterpillar is repellent to many predators because its favorite food is Southwestern Pipevine, which is chock-full of toxins.

Cochise County, Arizona, September 2020.

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More pipevine swallowtail caterpillars, from babies to big caterpillars to a chrysalis. 

In the first photo, you can see the spot above the caterpillar’s head where the hornlike osmeteria emerge when it wants to scare a predator away.  And in the middle photos, a better view of the actual threat display.

Often, but not always, the caterpillars take on a much darker color as they mature.  You can see that a couple of the big, sturdy caterpillars are a dark plum color with just a few red highlights.

The caterpillar climbing a wall, toward the end of the set, had formed the chrysalis by the next morning.  It started off yellowish green, and soon faded to a beige color that blended in with the wall.  Sadly, a storm blew the chrysalis away before the butterfly had a chance to emerge.

Have I mentioned that our yard was full of these little guys last summer?  So, lots of chances to watch them do their thing.

Cochise County, Arizona, September 2020.

[crowsandconverse-blog]

Time for another round of Nature Nerd Nick's cool critter Finds of the Week: a beautiful black swallowtail caterpillar (Papilio polxyenes) that was chowing down on some Queen Anne's Lace at work! These little guys love to eat plants in the carrot family and have little smelly horns called osmeteria that they use as a defense mechanism #lepidoptery #papiliopolyxenes #osmeteria