Two new species of the genus Eristalinus Rondani, 1845 (Diptera: Syrphidae) from the Gangetic Plains of Eastern India

Abstract. Two new species of the hoverfly genus Eristalinus Rondani, 1845 (Diptera: Syrphidae) are described from West Bengal, India, based on the adult morphology of both sexes and DNA barcode data. The new species, Eristalinus sapphirinus Roy, Naskar & Banerjee sp. nov., is characterized by its distinctive blueish black colouration, a strongly tapering head profile towards vertex in males, and the presence of an appendix on the loop formed by R4+5 wing vein. The second species, Eristalinus brunettii Roy, Naskar & Banerjee sp. nov., was initially collected as a morphologically divergent form resembling Eristalinus polychromata (Brunetti, 1923), but has now been confirmed as a separate species through integrative approaches. Phylogenetic analyses using Neighbour-Joining, Maximum Likelihood, and Bayesian methods, as well as species delimitation algorithms, consistently recover Eristalinus brunettii as a distinct evolutionary lineage. A brief diagnosis, description, distribution, images and barcodes for both new species are provided, along with a brief diagnosis and the first description of male terminalia for E. polychromata, and an updated taxonomic key to the Indian Eristalinus is presented.