Stress responses are essential for survival, coordinating behavioural, physiological and molecular adjustments that enable organisms to cope with challenges. Most research has focused on vertebrates, leaving invertebrate stress physiology comparatively underexplored, particularly in insects. In this review, we compare insect and vertebrate stress responses to examine what insects reveal about the evolution and ecology of stress regulation. There is a striking mismatch between the ecological and evolutionary diversity of insects and their representation in stress response research. Only 4% of recent empirical studies of stress responses focused on insects, with research concentrated in a small number of model and applied species. Despite major differences in neuroendocrine architecture, insects and vertebrates show convergence in several features of stress regulation, including rapid monoaminergic signalling, mobilisation of metabolic resources, neuroendocrine–immune interactions, and downstream molecular programmes associated with cellular protection and recovery. Vertebrates coordinate these responses through relatively centralised neuroendocrine systems such as the hypothalamo-pituitary-adrenal (HPA) and sympathetic-adreno-medullary (SAM) axes, whereas insects rely on more distributed interactions among biogenic amines, peptide hormones, neurosecretory tissues and visceral neural circuits, including interactions described in the proposed octopamine-adipokinetic hormone (OAH) axis. Developmental mode, life-history strategy and social organisation further generate variation in insects that is poorly captured by vertebrate-centred models of stress. We argue that cross-taxon generalisation is most informative at the level of ecological function rather than mechanistic equivalence. Rather than serving as simplified models of vertebrate stress physiology, insects provide complementary systems for testing how alternative regulatory architectures evolve under diverse ecological conditions.
