Parsley worms (aka. black swallowtail butterfly caterpillars) grow quickly, and the one living in my parsley plant is no exception. This caterpillar is packing on the grams at an impressive pace. You saw the photo I posted a few days ago. Now, check out how this guy has grown:

parsley worm on a parsley plant

I’m so proud.

But, it gets better. This parsley worm is now old enough to put on an impressive alarm display. This is what happens if you anger a parsley worm:

parsley worm threat display

Are you properly intimidated? No? Well, if you press your luck, this happens:

parsley worm threat display

parsley worm threat display

So fierce!

Those orange antenna things aren’t actually antenna. Instead, that’s the caterpillar’s osmeterium: a specialized scent gland that swallowtail caterpillars can spring from their heads when they sense danger. It’s a pretty intimidating display. Oh yeah, I totally jumped when this guy unleashed his osmeterium.

Supposedly, the osmeterium also release some noxious odor. Makes sense, since they are scent glands. But, well, I didn’t smell anything. Maybe I just didn’t get my nose close enough to smell that special angry caterpillar scent.

I’m also not sure what’s going on with that bubble of spittle in the last photo. The caterpillar was decidely not happy with me. So, maybe this is its second line of defense? Perhaps that stuff tastes horrible. So bad that a hungry bird would drop the caterpillar. I don’t know. I’m the curious sort. But, not so curious that I’m going to taste bubbles of angry caterpillar spit. Sorry.

Do you have black swallowtail caterpillars in your garden? You might, if you have parsley, dill, carrots or other Apiaceae plants in your garden.

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