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My, what a big osmeterium you have!

April 18, 2016

DSCN9675-002The Dainty Swallowtail butterfly (Papilio anactus), otherwise known as the Little Citrus Butterfly, was featured last year in a blog when it laid eggs on the lemon tree in our garden. The same thing must have happened this year because the lemon tree looks like it has been attacked by a chain-saw. Most of the leaves have been eaten back to the stem. The culprit was not difficult to find … a Dainty Swallowtail caterpillar (pictured left). While I was trying to dislodge the caterpillar from the leaf, a bright orange protuberance grew out from the caterpillar’s head (pictured below). It was its osmeterium.

DSCN9672-001The osmeterium is a defensive organ that looks like a snake’s tongue and is everted by the caterpillar when disturbed. The idea is to discourage predators such as birds and reptiles from attacking. This organ is found in papilionid butterfly species. In addition to the ‘fright’ value, the osmeterium emits an offensive odour to ward off spiders and insects that might otherwise consider the caterpillar as lunch.

So there is a new word for your vocabulary. Try using it in a dinner table conversation.

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