Species Delimitation in the Bark Louse Genus Neostenopsocus Liang & Liu, 2024 (Psocodea: Stenopsocidae) Based on DNA Barcoding

The family Stenopsocidae exhibits a rich biodiversity in China, yet species identification based on morphological characters remains problematic due to insufficient study and absent molecular data. DNA barcoding has been widely employed for rapid species identification in insects, particularly through standardized COI gene sequencing. In this study, we conducted species delimitation for <i>Neostenopsocus</i> in China based on the morphological characters and DNA barcodes, comprising 20 morphological species with 110 barcodes. We redescribed 13 species from China and proposed 39 new synonyms. This study supports the applicability of DNA barcoding for species identification in <i>Neostenopsocus</i>. The K2P distance between the morphological species of <i>Neostenopsocus</i> ranges from 0.0051 to 0.2040, with most exceeding 0.10. The maximum intraspecific divergence reaches 0.0778 in <i>N. nepalensis</i>. The external morphology of <i>Neostenopsocus</i> shows considerable structural uniformity, and the genitalia provide limited diagnostic value for species identification. Instead, the marking patterns of the head and forewing are considered to be useful for species identification. Therefore, delimiting closely related species demands an integrated taxonomy approach that combines extensive geographical sampling, detailed morphological analysis, and nuclear DNA data.