Insects feel persistent pain after injury, evidence suggests. Scientists have known insects experience something like pain, but new research provides compelling evidence suggesting that insects also experience chronic pain that lasts long after an initial injury has healed. Source 6b.
This is really interesting but also really disturbing. They had us do live insect dissections in college and assured us that the insects did not feel pain because they lack free nerve endings. It sat wrong at the time. Now it seems horrible.