Yellow-tailed Knifetail

Nesocordulia flavicauda is a medium-sized dragonfly with a metallic green body marked with bright lemon-yellow on the thorax and abdomen. The wings are transparent with dense venation, and the legs are long and slender. Males have a cylindrical abdomen that becomes broadened towards the tip and bears pale yellow appendages. The species is distinguished from other members of the genus by its characteristic abdominal markings and the form of the male abdominal appendages.

Nesocordulia flavicauda is endemic to southeastern Madagascar, where it has been recorded from forested freshwater habitats in the vicinity of Tôlanaro. Like other members of the genus, it is associated with streams and rivers flowing through native forest. Little is known of its ecology. Adults are rarely encountered, and the immature stages have not been described.

Nesocordulia flavicauda was described by Robert McLachlan in 1882 from Madagascar. In the same publication he established the genus Nesocordulia for the species, considering it intermediate between Neocordulia and Oxygastra but sufficiently distinct to warrant a separate genus. F. C. Fraser (1956) redescribed the species in his revision of the Madagascan members of the genus, refining its diagnosis and comparing it with the other species then recognised. Bernard and colleagues (2025) subsequently revised the genus, confirming Nesocordulia flavicauda as the type species and providing a modern redescription based on additional material.