August 02, 2019

Raising Black Swallowtail Butterflies, Part I

Despite baiting my top bar hive with an expired queen, ready-to-use combs, and repeatedly applying lemongrass essential oil, I was not successful in luring a swarm to move in and the beehive remains empty. But other buggy things are going on in the backyard that I thought you'd enjoy alongside me.

I started posting a #macromonday challenge on Instagram, where I post a photo of a flower bud and ask for your best guess at what flower it is. It just so happened that my parsley was in bud, and I saw something weird on it.
Can you spot the tiny yellow egg? 7/3/19
Black swallowtail butterflies nectar on many flowering plants but the female lays eggs only on plants the larvae can eat. Their host plants include dill, fennel, carrot… plants in the Apiaceae or Umbelliferae family. Over the course of a few days, I found a total of six eggs on one parsley plant. The photo below shows three eggs of different maturity. (Clicking on any photo will bring up an enlarged & enlargeable version.)
The egg turns almost black when close to hatching.  7/7/19
When hosts plants are not abundant, the mother butterfly will lay multiple eggs on one plant. With plentiful plants, she'll lay fewer eggs per plant. Being spread out increases the young's chances of survival. It's estimated that only 1% of eggs laid survive to become a butterfly. I planned to leave them alone, outside, and just let nature happen. But over the next few days some other insects came to call the parsley home. An ambush bug and a spider were particularly concerning.
Female black swallowtail nectaring on oregano, which happens to be a Halictus bee magnet.
When I was down 50%, I couldn't help myself. I set up an indoor habitat and brought 1 caterpillar and the last 2 eggs inside to raise. At this stage, the habitat was just a vase made out of a yogurt jar (shown below). Later, I put a large potted parsley plant in my honey-straining bucket and inverted a pop-up hamper on top (not shown).
The larva is easily seen through the shell.  7/11/19
After hatching, the caterpillar eats its shell. Apparently, it's a nutritious meal. I waited a long time then gave up and did not capture it on video.

Video of the caterpillar hatching from its egg.

Be careful when buying plants. The parsley in my garden came from the supermarket produce department, so I assumed it was non-toxic. [insert corny saying about ass-u-me] Not long after passing its first frass (poop) the first-born caterpillar died, and it dawned on me that the parsley wasn't clean. Neonicotinoids are systemic pesticides that wreak havoc on larvae. I'm growing exactly one organic carrot (a whole 'nother blog post) so transferred two day-old caterpillars to a carrot leaf, and off to Nick's Garden Center I went in search of new plants. They sell non-GMO 'Titan' parsley, and I found some bronze fennel. I read somewhere that Black Swallowtail caterpillars love it but mine opted for it last, only eating it when they were close to their final molt and ravenous.

The first instar (newly hatched caterpillar) is black with a tiny band of white, sometimes called the "bird poop mimic" stage. Though described as eating machines, you may not notice them eating much at this tiny stage. This caterpillar is on a carrot leaf. 7/12/19 
Their favorite food was the organic dill (sprigs) that I got from the produce section of the supermarket. In our dry environment, just laying the leaves in a plastic container isn't practical. They stay edible longer in a water-filled jar. A single leaf is plenty for the very young caterpillars. I just poked new holes in a paper towel and inserted more/fresh leaves as needed. The "cats" never wandered off the leaves – at least not until they were much older – but I put the vase in a container overnight to protect them from a very active spider season. Side note: Yoplait's Oui French yogurt is pricey but quite good!
Two first-instar caterpillars on a sprig of dill. Zoom in and you'll see lots of frass, the tiny specks on the paper towel. It's important evidence that your caterpillars are eating. 7/15/19
I found that the tiny ~2mm caterpillars preferred the tender dill but as they grew were more open to eating the tougher parsley and carrot leaves.
Just molted to 2nd instar. The caterpillar now sports orange spikes. 7/15/19

A caterpillar's cuticle (nonliving skin) doesn't grow with the caterpillar. Instead the caterpillar grows inside its skin. When it can't stretch anymore and becomes too small, the caterpillar molts, or sheds the skin. A caterpillar has spinnerets under its head, which it uses to produce silk to attach its prolegs (last set of feet) to the plant stem. The caterpillar does nothing (seemingly) for a full day and then shimmies out of its cuticle. It is actually fasting during the day of nothingness. After molting, typically it will turn around and eat the shed skin, leaving no evidence that could attract predators. In all, it will do this five times. Each stage between molts is called an instar, which looks entirely different from the last. The caterpillar is a bit pale when freshly molted and its color deepens as the skin matures, and within hours you should be able to identify the instar by its new look.

Older 3rd instar (7/17/19)

Younger 3rd instar (7/17/19)
As third instars, they started needing more leaves and as 4th they started getting curious and began to roam. This is when I gave them their first potted plants and put them in the honey bucket. Granted they were small plants, being just purchased from the nursery, but the cats ate the parsley down to nubs and left the bronze fennel untouched. As 5th instars, they lost their pickiness despite having a big, fresh parsley plant.

These caterpillars hatched within an hour of each other but one was always a day or two ahead of the other as they developed, so they consistently looked slightly different. (No, it's not because one's a male and the other's a female. We won't find out their sex until they're butterflies.)
4th instar caterpillars.
Mine are a black variation of Black Swallowtail caterpillars. Every website I referenced shows very green caterpillars at this stage. (I hope to share photos of the butterflies with @arizona_gardener, who raises all kinds of butterflies. He may be able to ID them even if they're a hybrid.)
Molting to 5th instar. 7/22/19
Molting starts with popping off their lenses (head capsule). Then, rather than crawling out of the old skin, the caterpillar shimmies it down, like taking off a pair of really tight pants. One-legged pants. With no hands.
It takes a half-hour or more for the eyes to become fully colored. If you look closely, you can see the dark yellow band which is the osmeterium.
When provoked, a forked gland may pop out of the caterpillar's head. The osmeterium "secretes strong-smelling defensive terpene compounds." Sorry, due to allergies and being perpetually congested, I can't tell you what it smells like. No, caterpillars aren't aggressive toward one another. The caterpillar on the left just had a different reaction to my poking them. Any more questions? LOL
The osmeterium is a defensive organ found in all papilionid larvae.
Pay attention now! If your fifth instar caterpillar stops eating and goes on a walkabout, wandering far from its regular grazing area, it's looking for a safe place to pupate. A sure sign is a "purge" or large, very wet blob of frass. No need to post a photo… you'll know it when you see it. And when you see it, it's go time! Some people drop the caterpillar into a paper bag or gizmo but I let mine wander and pick their own place, within the butterfly habitat that is. In addition to their potted host plants, I offered my caterpillars a paper bag and stalks cut from my day lilies. Both started their walkabouts in the evening, and I found them anchored to their chosen spots the next morning.
The 5th instar has no spikes.
Secured with a strand of silk, a girdle, this pre-pupal caterpillar is preparing for its final molt to become a chrysalis.

Prepupa is the last stage before forming a chrysalis. 7/27/19
After finding the caterpillars girdled in place, nothing happened for a good 24hrs. At least nothing visible was happening. Just as before, the chrysalis skin is underneath what you can see, so it must take that time for it to properly form. I kept checking and checking and finally just went to bed, and the next morning found the head and skin discarded below the chrysalis. Pretty amazing, huh? There's a really great video on YouTube if you don't believe me.
Head capsule and shed skin found on the ground below a chrysalis.
One chose a fennel stalk. The other one chose a day lily stalk, also green so both chrysalides are green. Unlike Monarch butterfly chrysalides which always look the same – super cool – swallowtail caterpillars camouflage their chrysalis somehow, so if it attaches to a brown stick the chrysalis will be brown. Caterpillars planning on going into diapause (in which case the butterfly won't emerge until next Spring) supposedly make brown chrysalides for better camouflage through the Fall and Winter.
About 24hrs later. 7/28/19
Depending on environmental factors, the butterflies will emerge in a week or two/three. To keep the pupa from going into diapause, one should keep the chrysalis somewhere where it will get at least 14 hours of light a day. Stay tuned for Raising Black Swallowtail Butterflies, Part II!

It's been a long time since I posted a long-format piece so if I was confusing or seemingly left something out, please leave a comment below.


Don said...

This is so cool! Thanks for sharing the whole process in one place. All my eggs/cats joined the 99% which bums me out, but next year I'll be a little more proactive. And thanks to your post, I'll know how to care for them!

HB said...

I wondered how your dill forest was doing @Don. I am sorry that the statistics were not in your favor. There's still one more generation to come this year so keep looking for eggs and caterpillars. The chrysalides they form will overwinter as chrysalides and emerge as next Spring's first butterflies. How cool is that?

Christina said...

Hi there! I realize this is an old post but thought I'd try reaching out for some caterpillar advice anyway, in case you are still checking comments!

I live in Wisconsin and it is mid-September - aka it's getting chilly with temps in the 40s overnight and 60s-70s during the day. I recently became obsessed with black swallowtails after discovering 6 cats on my parsley plant a few weeks ago. Unfortunately 4 of those 6 perished (I suspect parasitic wasps were to blame). The other 2 disappeared after getting very chubby so I'm hoping they made it to chrysalis/butterfly stage.

ANYWAY, a week or so ago, I spotted a couple black swallowtail butterflies lurking around the parsley (maybe from the original crew!?). After that, I then spotted about 7 eggs on the plant! With it being so late in the season, I was debating whether to leave the eggs outside and let nature take its course, or bring them inside. Still shaken over losing so many cats in the first round, I ended up bringing the whole parsley plant inside. I am worried I made a mistake though and that being in the warmth indoors will not trigger diapause, and by the time they make it to butterfly stage it will be too cold outside to survive. Do you have any advice? Should I move the chrysalis outside if/when they get to that point? (I am aware they can overwinter in chrysalis.) They just started hatching over the last 48 hrs...I've got 5 cats in the first instar, and 2 eggs still yet to hatch. So I have some time...

I appreciate any advice you could offer!

HB said...

You're right, @Christina, indoor warmth can trick them. If I were you, I'd put the parsley outside but in a protected setup. I use either a bucket with a mesh cover or I invert my pop-up mesh hamper over it. Just use something that will allow air circulation but screen out predators. Place sticks in the habitat when they're 5th instar, to keep them from forming chrysalides on the mesh. Best of luck with them. Come back and let us know what happens!

Christina said...

Thank you SO MUCH for responding! I am leaning heavily toward moving them back outside. I do have a protective enclosure for them. They are first instar now (also there are still 3 eggs that didn't hatch yet). I'm just worried moving them outside will throw their delicate bodies for a loop with the cooler temps, but maybe this is "kinder" than keeping them indoors where they're thriving now, but later won't get the message to overwinter in chrysalis...

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