Integrative species delimitation is commonly presented as a remedy for the limitations of single evidence classes, yet integration does not itself determine how conflicting observations should influence a taxonomic conclusion. Morphology, mitochondrial markers, genome-scale data, ecological differentiation and reproductive evidence can each fail for different biological or analytical reasons, and apparent agreement among evidence streams may reflect shared causes rather than genuine independence. This article develops a failure-mode perspective for integrative insect systematics. Instead of assigning evidence classes equal standing or privileging technologically intensive data, the proposed framework asks which processes can generate a misleading signal, whether those processes have been examined, whether sampling is adequate for the relevant spatial and biological scale, and whether nominally separate evidence streams contain genuinely independent information. Morphological evidence may fail through crypsis, polymorphism, sexual or maturational variation and inappropriate character selection; molecular evidence through marker inheritance, introgression, incomplete lineage sorting, threshold dependence and reference-library structure; and genome-scale evidence through population structure, gene flow, reticulation and model misspecification. Ecological and reproductive evidence add further information but remain conditional on geography, plasticity, contact opportunities and the scale at which isolation is measured. The resulting reliability-weighted model is explicitly proposed rather than empirically calibrated. Its purpose is to make taxonomic reasoning more transparent by linking the influence of each evidence stream to its diagnosed vulnerabilities, independence and unresolved uncertainty. Species hypotheses should therefore become more persuasive not merely by accumulating additional data, but by surviving targeted tests of the specific failure modes capable of producing the observed pattern.
