Chaetotaxy is an important character especially in mites and can be applied in species diagnosis, phylogenetics, ontogeny, and so on. Chaetotaxic ontogeny of Bdella was carried out through comparing both immature and adult descriptions of eight Bdella species, including a new species, B. xini sp. nov., from China. Based on these species, chaetotaxy changes in Bdella mainly focused on ventral hypostomal setae (vh), setae on palpal basifemur, aggenital setae (ag), genital setae (g), anal setae (ad) and leg setae.