Morphological and Molecular Identification of the Genus Diplonychus Laporte, 1833 (Hemiptera: Belostomatidae) from Eastern Ghats, India

T he present study investigates both morphological and molecular characteristics of the genus Diplonychus Laporte. Morphological identification was carried out by examining key diagnostic features such as the shape of the head apex, the posterior pronotal angles, the structure of the parameres, and the inner subapical region of the corium. Molecular characterization was performed using sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Based on integrative taxonomic analysis, the specimens were identified as D. annulatus, D. molestus, and D. rusticus. Phylogenetic trees were constructed to elucidate relationships among the species, revealing substantial interspecific genetic divergence, with raw COI genetic distances ranging from 14% to 19%. Specifically, the genetic distances between D. annulatus and D. rusticus, D. annulatus and D. molestus, and D. molestus and D. rusticus were found to be approximately 19%, 17–18%, and 14–15%, respectively. This study marks the first report of mitochondrial COI sequences for these three species from India, thereby contributing valuable molecular data to the taxonomic and phylogenetic understanding of Diplonychus in the region.