Invertebrates make up the vast majority of animal species and individuals, with growing scientific interest in their capacity for welfare-relevant experiences.
Invertebrate welfare is at the frontier of animal welfare science, where evolving evidence is challenging previously comfortable assumptions about the boundaries of moral consideration. The cognitive bias research in bees - showing they appear more optimistic after sugar rewards and more pessimistic after negative events - suggests emotionally-valenced states rather than merely reflexive responses. This is not proof of conscious suffering but is evidence that merits continued research and precautionary consideration. The enormous numbers of invertebrates affected by pesticide use, habitat loss and agriculture make this scientifically important.