I saw this on the dried out leaf of my D filliformis today. I've heard horror stories of caterpillars that eat the bases of dormant plants, and so I put this in a box until I can assess what it is and what I should do with it. If it eats those annoying other plants in the bog, it goes back in, if it's harmless it goes back in, if it shouldn't be in a bog in the first place it goes outside, and if it's dangerous Nepenthes eats it. Here's the picture.