Invertebrate welfare sits at the scientific frontier of animal sentience research. Insects, spiders, and other invertebrates comprise the vast majority of animal biomass and species diversity on Earth.
Invertebrate welfare represents a profound frontier for animal welfare science and ethics. If the probability of sentience in insects is even small, the arithmetic of suffering at scale is staggering given invertebrate population sizes. Emerging research provides evidence for nociception and behavioral indicators of pain-like states in multiple invertebrate groups. The precautionary principle applied to this uncertainty suggests taking reasonable steps to minimize potential invertebrate suffering in contexts where this is feasible. Priority areas include pesticide use, insect farming, and the treatment of crustaceans in food production. The field is evolving rapidly and welfare thinking must keep pace with scientific evidence.