Analgesic preference and injury behaviour in the cockroach Blaptica dubia

Abstract

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 wing-clipped Blaptica dubia preferentially consumed an ibuprofen-sucrose solution over sucrose alone, and whether injury altered the duration of abnormal behaviour.. Adult males were assigned to injured or sham-handled groups and completed 30-minute two-choice assays.. Choice between the analgesic, sucrose-only and neutral zones were recorded, as well as recording the duration of a range of abnormal behaviours. The experiment was repeated with vanilla scent added to both solutions as a masking agent.. Injured cockroaches did not show greater analgesic preference in either condition. Instead, the vanilla condition markedly reduced preference for the analgesic.. Injury strongly increased the duration of abnormal behaviours, with increases in the duration of body flexion, lateral swaying, and wing fluttering, while wing-directed grooming was rare but showed a tendency for increases when injured. These findings provide no evidence that injured B. dubia actively seek an orally delivered analgesic under the conditions tested. However, injury produced clear and sustained behavioural disruption consistent with an internally driven aversive or discomfort-related state, highlighting both the methodological challenges of adapting voluntary analgesic assays to insects and the welfare relevance of injury in B. dubia.