Rearing and observation of immature stages of the hoverfly Microdon katsurai (Diptera, Syrphidae)

The hoverfly Microdon (Chymophila) katsurai Maruyama et Hironaga 2004 was speculated to be a myrmecophilous species associated with the ant Polyrhachis lamellidens based on observations of adults near the ant nest. However, there have been no reports regarding the observation of immature stages of this species in association with P. lamellidens. For the first time, we found three M. katsurai larvae inside a P. lamellidens nest and conducted rearing experiments on the larval M. katsurai. P. lamellidens workers did not show any inspection or attack behavior against the M. katsurai larvae under rearing conditions, suggesting that M. katsurai larvae can survive inside a P. lamellidens nest. Although no predatory behavior by the M. katsurai larvae was observed, all the M. katsurai larvae pupated and emerged in a rearing environment. The dorsal surface of the larval M. katsurai has a distinct pale green color with a uniform reticular structure. The puparium of M. katsurai shows several morphological features that are characteristic of the subgenus Chymophila. We conclude that M. katsurai is likely a myrmecophilous species that utilizes P. lamellidens as a specific host and that classification of M. katsurai based on puparium morphology is concordant with that based on adult morphology.