Odd soft bug

Can someone tell me anything about this little yellow guy that was brought to me by a nephew. He told me that when he found it, it was moving around on multiple legs and was bright yellow with a green edging. What he brought to me looked like a rolled up isopod (pill bug) a hard brown colored ball. I left it along for a week to see if it would open up and get active. It never did so I took a needle to it and found the some yellow thing you see here inside the brown case which is also pictured. It is very soft with hairs around its margin that have a small amount of green on them. I cannot see any legs or even a mouth but it does curl slightly when touched. Is it a larvae of some type or maybe a phyllid.