The welfare of invertebrate animals has historically been disregarded, but accumulating evidence of nociception, stress responses and learning in insects and other invertebrates is prompting serious scientific reconsideration.
The scale of invertebrate life on Earth makes this one of the most ethically consequential questions in welfare science. If insects experience something morally relevant - even a fraction of the richness of mammalian experience - the number of individuals affected by agricultural practices (pesticide exposure, habitat loss, mass rearing for food) dwarfs all vertebrate welfare concerns combined. The scientific evidence is not yet conclusive for full sentience, but the precautionary principle applies powerfully: practices that cause likely suffering to many individuals warrant precautionary reform even absent certainty. Welfare science for invertebrates is at the frontier of the field.