First morphological description of the larval stages of three Microtendipes species (Diptera, Chironomidae) from South China with molecular confirmation

This study presents the first integrated morphological and molecular characterization of larvae from three Microtendipes species, Microtendipes baishanzuensis Song & Qi, 2023, Microtendipes robustus Song & Qi, 2023 and Microtendipes tuberosus Qi & Wang, 2006, collected from subtropical streams in China, providing important insights for advancing Chironomidae taxonomy. Using detailed morphometric analysis (head capsule ratios, mandibular pecten length, and striae counts) in conjunction with mitochondrial COI barcoding, we established larval–adult associations and differentiated these species from their congeners. Microtendipes baishanzuensis is characterized by a brownish head capsule with distinctly paler median teeth compared to the lateral teeth, the longest mandibular pecten within the genus, the highest number of body striae, and an exceptionally anteriorly positioned ring organ. Microtendipes robustus is distinguished by a uniformly dark brown mentum, remarkably wide ventromental plates, the most variable striae count, and a medium-sized mandibular pecten. Microtendipes tuberosus exhibits a uniformly dark brown mentum with median teeth conspicuously shorter than the second lateral teeth, the smallest body size in the genus, the shortest mandibular pecten, the fewest striae, and the most posteriorly located ring organ. A revised larval key for Chinese Microtendipes is presented, improving freshwater biomonitoring and addressing challenges associated with cryptic diversity.