Flexible Self-Protection as Evidence of Pain-Like States in House Crickets

The possibility that insects experience pain is a frontier question at the intersection of animal behaviour, comparative cognition, and philosophy of mind. Interest has been fuelled not only by anatomical discoveries but also by expanding behavioural and comparative evidence. Under leading frameworks, the most informative behavioural indicators of pain-like experience include flexible, targeted responses to harm that suggest more than stereotyped, reflexive withdrawal. Here we tested for such responses in the house cricket ( Acheta domesticus ), a species of both evolutionary and commercial importance. Using a fully blinded, within-subjects design, we applied either noxious heat, tactile contact, or no contact to a single antenna under both lower- and higher-stress environmental conditions and recorded subsequent grooming behaviour. Crickets were significantly more likely to groom the noxiously stimulated antenna, and did so for longer durations, than under control or tactile treatments. Grooming also showed a distinct temporal profile, with elevated activity sustained across the early observation period. Environmental condition and sex had no effect, indicating that self-protective grooming was expressed consistently across contexts and sexes. These findings provide robust evidence of flexible, site-directed self-protection in Orthoptera, addressing a key gap in the evidence base for pain-like states outside vertebrates. Such evidence strengthens the case for precautionary consideration of insect welfare, while also bearing on the broader scientific question of how felt experience is distributed across the animal kingdom.