What does a pupating mealworm look like?

[la dee da]

We have a bunch of mealworms living in oatmeal. I already changed their potatoe once before, and the new one looks like it needs to be changed. Today I picked up a half and heard a little pop. When I looked at the bottom I saw yellow stuff that had connected the potatoe to the bottom of the bucket. I think I might have killed some pupating mealworms (needless to say the ones nearby weren't happy with me). I put the potatoe half back, but I was wondering if anyone knows what the yellow stuff is.

 

[centrarchid]

http://www.flickr.com/photos/71524570@N00/14529928/

 

[la dee da]

The yellow stuff was that color, but it was all stuck together also. I guess I'll know soon enough, thank you!