Genome-scale data have transformed insect systematics by exposing population structure, cryptic lineages, introgression, discordant genealogies, and phenotypically inconspicuous divergence at unprecedented resolution. Greater resolution, however, does not make species inference self-validating. Species delimitation still requires decisions about what biological process produced an observed partition, whether apparently corroborating evidence is genuinely independent, and whether evidence supporting lineage separation is sufficient for reproducible diagnosis and naming. This critical review evaluates these problems across coalescent delimitation, phylogenomics, gene flow, reticulation, morphological and ecological discordance, and integrative taxonomic practice. The evidence shows that population structure can mimic species boundaries, gene flow can coexist with lineage integrity, mitochondrial and nuclear histories may diverge, diagnostic morphology can depend on sex or developmental condition, and genomic scale does not eliminate model or sampling error. The review therefore develops a proposed distinction among evidence detection, process interpretation, lineage delimitation, diagnostic corroboration, and nomenclatural assignment. Under this synthesis, conflict is not treated as failed integration but as information about competing biological or analytical explanations. Evidential strength depends not simply on the number of datasets agreeing, but on whether they interrogate partly independent biological dimensions and survive explicit alternative-process tests. This approach is intended as a critical framework for more transparent insect taxonomy under increasing genomic complexity rather than as a universal species criterion.
