While Microstylum oberthurii Wulp, 1878 is a common species of robber fly in Taiwan, there are few records of its natural history. In the present study, the author describes the oviposition behavior of M. oberthurii, as well as the behavior of newly eclosed adults, based on seven years' worth of field observations. In Taiwan, M. oberthurii adults are known to occur from June to August. Photos of M. oberthurii observations are provided, including a newly eclosed adult, oviposition, eggs and a first-instar larva.