Black swallowtail caterpillars

After a big morning storm on June 11, which included plenty of hail, we spent a lot of time in the garden checking on the flowers and the caterpillars. Not many flowers were blooming yet, which may have worked in our favor: some common milkweed and cup plants had a few ripped leaves from the hail, but most looked just fine.

The monarch and American lady caterpillars were wet and recovering where they usually reside, and then we found something somewhat unexpected: five black swallowtail caterpillars.

It wasn’t completely unexpected because they were all on Golden Alexanders, which is a host plant, and I had been looking for them for a couple weeks. (I saw a butterfly on May 12, and a caterpillar last year, so I knew it was a possibility.) But I was quite surprised to find five!

large, mostly white caterpillar, with black and yellow stripes, along a flower stem with its mouth at the blossom

a little smaller, more yellow, resting on a leaf

two mostly yellow, spiky caterpillars in the flower blossom, eating

The fifth looked strange; maybe it had been hurt during the storm?

a caterpillar upside-down, possibly wedged between two flower stems

I kept checking for them after that day, and two were visible for more than a week. Here are photos from one evening:

a skinny, smooth, green caterpillar with black stripes that have yellow dots, along the bottom side of a half-eaten leaf

similarly sized caterpillar viewed from the front, holding a leaf in its front legs to eat it

Same caterpillar from the side, looking guilty (though of course that is just my funny interpretation):

still holding the leaf, but the patterns on its head make it look like the caterpillar is hiding behind its hands in embarrassment

This was the last night I saw any of these caterpillars. I don’t know enough about the life cycle of black swallowtail butterflies, yet, to know whether these caterpillars moved away to pupate, or whether they were more likely eaten by birds, wasps, or something else.


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