DNA barcoding has become a central component of insect identification, biodiversity inventory, reference-library construction and accelerated taxonomic workflows, yet its evidential meaning changes substantially according to the question being asked. A COI sequence may support specimen identification, reveal discordance requiring taxonomic investigation, generate a preliminary molecular cluster, or contribute to species delimitation, but these functions are not logically interchangeable. This evidence-mapping review examines contemporary insect-systematics literature through the linked problems of barcode resolution, reference-library dependence, biological discordance and integrative use. Across taxonomically and geographically diverse applications, high identification performance frequently coexists with barcode sharing, deep intraspecific structure, algorithm-dependent molecular operational taxonomic units and incompletely sampled reference libraries. The evidence therefore does not support a universal judgment that barcoding either resolves or fails to resolve insect species. Instead, resolution is conditional on taxon history, sampling design, reference quality, marker properties and the inference being attempted. A proposed distinction is developed between identification concordance, cluster concordance and delimitation sufficiency. Biological processes such as introgression and incomplete lineage sorting are further separated from nuclear mitochondrial sequences, sequencing artefacts and reference-data errors because superficially similar barcode discordances require different tests. The resulting evidence map positions DNA barcoding most strongly as a scalable identification and hypothesis-generation system whose taxonomic force increases when molecular patterns are adjudicated against independently informative morphology, geography, ecology, life-history information, additional loci and curated vouchers.
