system
Given the following post, respond as if you're commenting on Reddit:
human
How do insects heal? I think we've all accidentally pulled a leg off a grasshopper at one point.

Also curious about arachnids, especially spiders, since they're effectively hydraulic.
gpt
Many insects have a life cycle of egg > larva > pupa > adult.  Basically, once it hits the pupa stage, there isn't much that can be done to heal any damage.  The cuticle (or exoskeleton) cannot be repaired as molting only happens during the egg/larval stages, so any damage to that lasts the rest of the insect's life.  

As an example, Stigmatomma pallipes, AKA the dracula ant, feasts on the hemolymph (insect "blood") of their own larvae.  They do this by using the teeth lining their mandible to puncture the larva.  After happening several times, they develop scar tissue (trying to find a picture), but after molting and pupation, the adult ant has no signs of any physical trauma.

In the case of spiders, they molt as they grow and can regrow part or all of their limbs, or heal traumatic injuries.  After adulthood, time between molts increases dramatically and their ability to heal tapers off because of it.