Scientific evidence for insect sentience has grown significantly in recent years. Understanding the current state of evidence helps inform precautionary welfare approaches to the world's most numerous animals.
Insect sentience is genuinely scientifically uncertain but the evidence has strengthened considerably in the past decade. The discovery of pessimistic cognitive bias in bees - analogous to the depression-associated cognitive changes seen in vertebrates - suggests something beyond simple reflex responses to noxious stimuli. Opioid-like analgesic systems in insects imply evolutionary pressure to reduce pain experience, which would only be selected for if the experience matters to the animal. If insects are sentient at even a modest level, the implications for ethics and policy are profound given their numbers. The application of precautionary principles to insect welfare does not require resolving the philosophical question of insect consciousness - it requires taking the uncertainty seriously enough to minimize unnecessary suffering in the world's most numerous animals.