The ethno-veterinary knowledge provides a range of potential herbs with acaricidal properties (Ghosh et al. 2006). Stemona plants, which are well-known in Thailand and Southeast Asian countries for their insecticidal properties (Chuakul et al. 1996; Pilli et al. 2005; Greger 2006), are interesting because of their anti-tick activity. There are, however, at least eight different species of Stemona spp. with indistinguishable root shape and are known under the same vernacular name ‘‘Non Tai Yak.’’ Due to different chemical fingerprints and contents of bioactive constituents, each species was tested for their anti-tick activity.