Analgesic preference and injury behaviour in Blaptica dubia

Insects are increasingly recognised as behaviourally complex animals, yet whether they experience pain as an affective state beyond nociception remains unresolved. Voluntary ingestion of analgesics by injured individuals has been proposed as a key but largely untested criterion for evaluating insect pain. This study tested whether Blaptica dubia cockroaches injured by wing clipping preferentially consumed an ibuprofen-sucrose solution over sucrose alone, and whether injury altered rates of abnormal behaviour when individuals were not feeding. Adult males were assigned to injured or sham-handled groups and completed 30-minute two-choice assays, with behaviour scored at 30-second intervals across analgesic, sucrose-only, and neutral zones. We also repeated the experiment with vanilla scent added as a masking agent to both analgesic and sucrose-only solutions. Injured cockroaches did not show greater preference for the analgesic solution either in the presence or absence of the vanilla masking agent. Instead, strong differences emerged between experimental conditions, with individuals in the vanilla-flavoured condition showing reduced feeding engagement overall. We therefore have no evidence that injured cockroaches actively seek out analgesics. We suggest methodological refinements are required before we can absolutely reject the possibility of analgesia preference and so the sensation of pain. In contrast, injury increased persistent abnormal behaviours, including abdominal pulsations, wing-fluttering, wound-directed grooming and body flexion. Therefore, injury produced clear behavioural disruption consistent with an internally driven aversive or discomfort-related state, highlighting both the challenges of adapting voluntary analgesic assays to insects and the welfare relevance of injury in B. dubia.