Black Swallowtail Caterpillar (parsleyworm)

I found a beautiful black swallowtail caterpillar on the edge of my garden two days ago. I picked him up, and he did not use his defence mechanism (which I was not aware that they even had one at the time) and put him in a little terrarium I made for caterpillars. I identified him the next day and clipped some small parsley shoots (I had just previously havested all my parsley to feed to my ginuea pigs so it wasn't much) I had in my garden and gave them to him. He ate them FAST! I didn't have anything else to give him so I went to wal-mart and picked up some parsley. When I. rinsed it off very well and gave it to him, he nibbled off one leaf and started behaving oddly. He seemed to have a boost of energy and crawled all over the parsley, stopping at the edge of the leaves to try to eat. I thought maybe it wasn't to his liking compared to my garden parsley when he seemed to throw a 'fit' by coiling his upper body towards his rear (much like they do in defense) but in a matter of minutes he was coiling wildly, rolling all over the terrarium. He was secreting a liquid from his mouth and rear-end. I removed the parsley and picked him up when his horns portruded from his head and the odor overwhelmed me, so I placed him outside for a few minutes. When I brought him back in, he was a lot less active. I let him alone and went to check on him this morning and he was unresponsive.

My question is, did he die due to possible insecticides in the parsley, or was there something wrong with him in the first place since he didn't defend himself when I first picked him up?

I read online that you can feed them parsley from the store if you don't have any of your own, but I don't think I'm going to do that again after this...

I just placed him in the sun and his head is still moving around but the rest of him isn't moving, so he isn't quite dead yet, but can't be too far off. He has sticky green spit all over is face and legs I tried wiping off. Is there any hope for this little guy? If so, what can I feed him besides parsley?

he might be trying to make a cocoon?

I don't think so. He's definitely dead.. I've convinced myself that the parsley was sprayed with pesticides so much that there was some in the plant itself. =( poor caterpillar.