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Staff Hobby - Butterfly Rearing Part 2

If you missed part 1, don't forget to read that article too, here.


So last time we discussed my hobby of raising Monarch caterpillars to butterflies and as promised, I'm back to discuss Black Swallowtail (BST) caterpillars and butterflies.



What you've probably seen are the actual butterflies fluttering around. They're mostly black with either a dominance of blue or a dominance of yellow on their wings. This species is much easier to tell the males and females apart compared to Monarchs. "Lots of yellow it's a fellow." The males have a dominant bit of yellow on their wings, where as the females have mostly blue. See if you can tell the difference below.



The lifecycle of BSTs is the same as Monarchs. It starts from egg, to caterpillar (larva), to chrysalis (pupa), and to butterfly. The timeline, however, is a little more difficult to estimate, specifically at the chrysalis stage. The egg stage lasts 3-5 days, caterpillar stage about 3-4 weeks, chrysalis stage 10 days or more, and adult butterfly stage is 1-2 weeks. The reason the chrysalis stage is not easily determined is that this species of butterfly does not migrate; it overwinters. This means it goes into a type of hibernation if it senses cold weather or fall approaching. So I like to say black swallowtails are on their own time clock when it comes to that stage. People who have raised them in the past said they've had some eclose (come out of chrysalis) as many as 2 years after it pupated. We've had a few that have waited over a year to come out and grace us with their beauty.


BST female butterflies lay their eggs on parsley, dill, fennel, rue, carrot tops, and Queen Anne's Lace. They will not eat milkweed like the Monarch caterpillars eat. What's really neat about the caterpillar of the BST, is they hatch and are black with a white stripe. As they grow and molt, they change colors to green, black, and yellow. Monarchs are the same color throughout that whole stage. See if you can spot the egg in each of the first two pictures below.



In addition, when the BST pupates, they look like a wilted or wadded up leaf, and can be green or brown. It's not really understood why some choose green or some choose brown, but it's thought to be a type of camouflage depending on where they decide to pupate. So if they pupate on a stick, they'll go brown, or if they pupate on a leaf or green stem, they'll go green. This doesn't happen 100% of the time, but it does seem to happen a lot. People thought maybe one color was males and one color was females but's definitely not the case.



Like Monarchs, the BST caterpillars also have parasitic bug they can get. This one is a wasp. The wasp will lay its eggs on the caterpillar, and once the eggs hatch they burrow into the caterpillar. They'll then come out after the caterpillar pupated. There is no warning that the caterpillar was parasitized though, and the wasps can overwinter too!



Lastly, like most butterflies, the BST adults like all sorts of color flowers for nectaring. Zinnias are the biggest hit.



I'm hoping you enjoyed my two-part Staff Interest of butterfly rearing. Again, if you didn't have a chance to read the first installment, click here.