Caterpillar Mandibles Damaged? Please, please help!

[chrestien]

My boyfriend found a Monarch caterpillar in the middle of the sidewalk 11 days ago. We live in Brooklyn and he was concerned for it, so he brought it home. We spent the next afternoon tracking down Milkweed and Thomas (the caterpillar) ate up a storm for the first 6-7 days!

On Thursday, I gave Thomas a Milkweed clipping that still had one of the spiky pods attached to it. When I checked on him, he had eaten off several spikes and seemed to be enjoying himself. The next day, I came back to find he had stopped eating. I washed the rest of the milkweed and offered it to him, thinking maybe he didn't like the ones from Thursday. He latched on to the edges of a few different leaves and made munching motions for a while, but never actually bit through any of them.

On Saturday we bought two tropical milkweeds, thinking maybe the other species' leaves were too hard for him. Once again, he latched on and made the motions of eating, but was unable to penetrate the leaf. He hasn't eaten since Thursday and is beginning to lose weight.

He clearly wants to eat, but can't. When he latches on to the edge of a leaf, he'll munch down the side ferociously and make sawing motions with his head, but can't seem to bite through. I've boiled a few leaves and used the nutrient-rich green water left behind to feed him. He goes crazy for the it. I've also ground up some leaves into a chunky paste and while he seems interested, doesn't eat it.

We have grown quite attached to him and the only other person I've found describing this behavior online is wildmustng87 on this forum a year ago. http://monarchwatch.org/forums/viewtopic.php?f=6&t=1914 I've PM'd them, but haven't heard back yet.

Is it possible he damaged his mandibles? What can we do?
Please help us help Thomas!

Also:

Yes we are sure we have milkweed.
He is still quite active.
There are no signs of bacteria.
He wants to eat and is trying to eat.
Even caterpillars with parasites continue to eat!

[Mona Miller]

Usually by now they are ready to pupate. Usually only takes 7-10 days to go from caterpillar to pupa.

I'd go back to the originial milkweed, if you think it still needs to eat. Common milkweed is a lot less toxic than tropical. I've gone from tropical to common, but haven't tried to take them from common to tropical.

If you think its mouth is gummed up, trying spraying that area with some water. Water loosens all kinds of things.

BTW, they love milkweed pods and the immature seeds.

[chrestien]

He drank up the milkweed-infused water like crazy last night.. would that de-gunk his mouth? I saved the rest of it and will be giving him more in a second.

The problem started on the original milkweed, of which there is no more. It took forever to find the common milkweed and the only store that had it is out. We got really lucky finding the tropical, and he seems very attracted to it.

It's so heartbreaking to watch him try and try to eat! The leaves he's tried to munch had markings down the side from his jaw, but they were never actually cut through. If you or I pressed a fingernail to a milkweed leaf causing damage to the palisade parenchyma without breaking the skin, that's exactly what it looked like.

[chrestien]

I just dripped some of the water down the stem to where he is resting. He immediately lapped it up and looked for more. I'm hoping it helps.

(Side note: He's 2 inches fully stretched out, so I know he's not molting)

[chrestien]

Still not eating. What seems to be his favorite leaf (he keeps going back to it and chilling out/trying to eat) has mandible marks along both sides. Looks like he almost cut through it in one place.

Any suggestions? Ideas? Thoughts? Concerns? We would really appreciate it!

[Mona Miller]

http://www.monarchwatch.org/biology/cycle1.htm
Larva (Caterpillar; 10-14 days)
It is during this stage that Monarchs do all of their growing. They begin life by eating their eggshell, and then move on to the plant on which they were laid.

When the caterpillar has become too large for its skin, it molts, or sheds its skin. At first, the new skin is very soft, and provides little support or protection. The new skin soon hardens and molds itself to the caterpillar, which often eats the shed skin before starting in anew on plant food! The intervals between molts are called instars. Monarchs go through five instars (see photo). Approximate length of body at each stage:
1st instar, 2-6mm;
2nd instar, 6-9mm;
3rd instar, 10-14mm;
4th instar, 13-25mm;
5th instar, 25-45mm.

Basically, 45 mm is 1.7717 inches so if your caterpillar is about 2 inches then it is ready to pupate. Pupation is when they change to a chrysalis. Molting is when they shed their skin to go from one instar to another.

http://www.evansonart.com/monarchraise.html
This has some good info on raising Monarchs.

http://www.mymonarchguide.com/2007/05/r ... llars.html
This is another good website on raising Monarchs.

[Mona Miller]

Still not eating. What seems to be his favorite leaf (he keeps going back to it and chilling out/trying to eat) has mandible marks along both sides. Looks like he almost cut through it in one place.
Any suggestions? Ideas? Thoughts? Concerns? We would really appreciate it!

If the caterpillar is 2 inches, it might be ready to pupate. At that time, they stop eating and will roam around the container for a while. Then, make a silk mat, eventually hang upside down, and then pupate.

[chrestien]

Thank you for the responses, but it's been 5 days and he has yet to J. He's lost all the weight he gained during the first 6-7 days. He periodically attempts to eat, then gives up after a few minutes. The attempts are emphasized by the teeny marks (not true bite marks, just cell damage under the skin) to the edges of leaves.

Any time I place the milkweed pulp or milkweed juice I made next to him, his filaments perk up and he becomes quite active. He drinks the juice and sucks at the pulp, but doesn't eat it.

[Mona Miller]

I wonder if you could take some thing and try to put the food further back into its mouth. I know this is frustrating. I'll say a little caterpillar prayer for Thomas. Sorry.

[chrestien]

I took a video with my shoddy camera.. but it should give you guys an idea of what's happening.

Thomas has his very own plant, this was a temporary set up for the video. Prior to making this video, I spread some milkweed pulp onto his leaf. It's not frass!

http://s25.photobucket.com/albums/c67/PommesBleues/?action=view&current=MVI_5020.mp4

[Mona Miller]

It looks like it is trying to eat, but isn't able to. I've never seen this. I'm still praying for him/her. It could be a Thomasina.

[chrestien]

I've figured out what is wrong with Thomas.. When he was eating the spikes on the pod, they secreted a lot of milk. The milk in milkweed contains 1-2% latex. Several caterpillars die in the wild from too much exposure to the milk because it literally glues their mandibles shut. (This is also why they bite the stem of a leaf before munching it... my disconnecting it from the main stalk they cut off the leaf's supply of milk)

Thomas' right mandible is fine, but is left doesn't fully extend. Now what? What do I do to unglue it?

[Mona Miller]

All I know is that some water will help soft it. Give him a bath, but do it carefully.

[Kestrel]

Thanks for posting the video. So, what happened?