Kris0p
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Black swallowtail caterpillar leaves plant and dies

I've been raising several black swallowtails this year for the first time. I have a net enclosure. I have a potted plant sitting in a Styrofoam tray, on a paper plate. A couple cats have left the plant, roaming on the tray or plate. Both times, they stayed there a day or two. I was concerned he couldn't get back on the plant and tried to put him back. Would fall off onto the dirt below or the plate below. Didn't want him getting buried in the dirt, so finally put him back on the plate. The first time, the cat just shriveled up and died. This time, I left a parsley leaf next to him in case he was hungry, but he didn't eat it. He looks like he is dying, as well. Am I doing something wrong?? I want to raise them successfully.

Also, I have had two batches of eggs laid on my dill and parsley. The first set of cats were mostly eaten by predators, I guess. I tried covering the area with tulle netting, but didn't seem to stop anyone. I have more eggs now. How can I protect them outside, and enjoy them there?

Thank you!!

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applestar
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My kids and I raise Monarch butterflies, black swallowtails, and incidental other cats (last year, we found question mark caterpillars on elm) every year.

How old were they when they left the plant? When butterfly cats reach maturity after full cycle in the 5th instar phase, they typically do leave the plant to find a place to make chrysalis. Also, note that cats sometimes leave to molt in a quiet place between instar phases.. They are fragile at this time because their cells are disorganized and shouldn't be disturbed. They will stay still as if dead for about 24 hrs.

I find that it is best to collect eggs and 1st instar caterpillars and raise them indoors because otherwise, the predators infest them. It's heartbreaking to raise monarch caterpillars to the final chrysalis stage, only to have them go limp as they try to make their chrysalis and tachnid fly maggot ooze out.

If you want to keep them safe outside, I understand the best method is to make plant sleeves out of tulle that cinch tightly closed on top and bottom, and enclose the caterpillar and the plant. You need to check every day and re-position the sleeve and the caterpillars so they don't run out of food.

If the cats shrivel and die in earlier instar phase, it's usually some kind of disease. Very often, they have been infected with the popular organic insecticide Bt. They could also have been affected by other organic or chemical pesticides and herbicides. If you live near gypsy moth infestation or large fields of corn, beans, etc. that are affected by pest caterpillars, they may use mass aerial spray with crop dusting airplane. Apartment complexes and some condos, townhouses, HOA etc. contract regular spray schedule with broad-spectrum pesticides inside and outside.

There is also a parasite that infects monarch butterflies, they are transmitted in spore form by infected adult female butterfly to their eggs, and there's nothing much you can do. It's possible similar parasite affects black swallowtails.

It's sometimes a challenge, but extremely rewarding to raise butterflies. I wish you lots of luck!

Kris0p
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Thanks for your immediate responses to my concerns. I don't have the chrysalis in the sun in the den, so I will move him. If he doesn't come out soon, what do I do?

As for the caterpillars dying, they have been about second or third instar. I'm guessing they may have left the plant to molt. I tried to move them back to the plant, and they weren't able to stay on because their cells were disorganized as you said. I didn't realize this and will keep hands off and leave them alone. Thought they couldn't find their way back and I probably made things much worse. I guess it is also possible they had a disease. As for the plants they were hatched on, I grew the dill from seed, and the parsley came from a garden store sold as an herb. Other cats have fed on the parsley, I think. If it had been treated with an insecticide, would that wash off in the heavy rains we have had? If I purchase plants, can I wash them before feeding my little friends?

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applestar
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Here's the label from Thuricide, which I suppose is typical, though "professional" grade product may be a little different.
:arrow: https://www.bonide.com/lbonide/backlabels/l802.pdf

Since it says it can be applied up to day of harvest, it's possible for store bought herbs and vegs to be contaminated. It also says to re-apply after heavy rain which seems to mean it can be washed off, and it says to apply at weeky intervals. With potted plants, I would then grow the plants for a week or two before feeding the cats with them.

Note that they also eat fennel, celery leaves and carrot tops, as well as Queen Ann's lace leaves which you may be able to find unsprayed roadside sources for. Introduce new foods in combination with what they have been eating. Sometimes, they won't recognize/eat a different plant from what they are used to.

Kris0p
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The plant I brought in for this little guy has been in the ground awhile, and we have had heavy rains. I brought in the plant he hatched on. His brother is nice and big from the same plant. I will make a point to wash off any plant I get, just to make sure. I have been avoiding grocery store carrot greens, thinking they likely have been sprayed with something.

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applestar
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If you suspect a caterpillar of having a disease (relatively slow development could be a sign). Sick cats also often have diarrhea - and can transmit the disease via body fluids, so it's best to isolate it from the others.

I like using quart size deli containers and clear/translucent large beverage cups lined with 1/2 paper towel folded in half (1/4 "square"). For good air flow, Make holes along the base of the side wall and in the lid. With bev containers, push the straw hole outward so the cats and butterflies don't get snagged on the pointies. For small cats that may be able to crawl out of the hole, place a square of cheesecloth over the opening and then put the lid on.

BST's will make chrysalis on dill stalks and carrot leaf stems, but put a stick or bamboo skewer in there if necessary. If the silly things make a chrysalis on a stem that isn't strong enough to support them, cut the stem above and below the chrysalis and tape to the lid or high up on the side of the container by the stems. (there should be sufficient clearance for their wings to spread out) Same idea if they attach themselves to the paper towel or too low on a stem.

Paper towel should be replaced every day and twice a day when they get bigger.

sallyjoan
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I have just had a few Black Swallowtail fully grown caterpillars act like they might form a chrysalis then fold over and half hang down from their spot and die. This is the first time I have seen this. Very strange, especially since they are so big and healthy looking. I'm growing them in a small butterfly house to keep predators away. Then I release them when they hatch. Any ideas why they might behave this way?

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applestar
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I have seen this with Monarch butterflies. Did it have diarrhea or regurgitate before doing this? If so, then it was probably a bacterial infection -- Bt can cause this kind of illness and death, but it could have been something else as well.

If not, it might be infested by a parasitic predator like tachnid fly. Be sure to observe the remains and if you see any mucus or web/silk like string hanging from it, then search carefully in the enclosure for brown fly pupae. You don't want the fly hatching in there -- especially if there are more than one in male/female pair to mate and lay eggs on cats inside the butterfly house. A large caterpillar can host 2-3 fly maggots.



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