Why do insects curl their legs up and roll on their back when they die?

Question

ballistickmafia · Answer

Would it have something to do with their flexors and extendors?

ramirocruzo · Answer

The most common explanation given for why bugs die on their backs is something called the position of flexion. A dead (or near death) bug cannot maintain tension on its leg muscles, and they naturally fall into a state of relaxation. In this relaxed state, the legs will curl or fold up, causing the insect or spider to topple over and land on its back. If you rest your arm on a table with your palm up and relax your hand completely, you will notice that your fingers curl slightly when at rest. The same is true of a bug's legs.

anonymous · Answer

Simplified explanation:
You can think of it as pruning. When they die there body lacks fluid in the tissue causing the muscle to contract together, thus causing them to fold and close up and roll on their backs!