I have seen how some insects can regrow lost legs, especially if the loss occurs at a young age. What I find really interesting is how the new legs grow in the stick insects. When the insect has its next molt after the loss,
a tiny, curled-up leg emerges. I think it must develop under the exoskeleton all coiled-up, only to be released when the insect sheds. Then, it gradually straightens and grows with each subsequent shed until it reaches normal size.
I wonder if the baby stick insect is similarly coiled inside its egg before it hatches. I'd like to watch one hatch someday.
Regenerated "embryonic" leg. Click image to enlarge. You can see the toes.
UPDATE: See part 2 of this post here.