The Mesostigmata is an order of Subclass Acari either parasiting to diverse invertebrates or free-living predatory in terrestrial ecosystem. Phoresy is one of the unique behaviors of wingless arthropod dispersal by attaching winged arthropods. We collected mites attached on the dorsal part of abdomen adult sciarid fly, from mushroom culture. The mites were identified as Arctoseius cetratus Sellnick, 1940 in the family of Ascidae. Arctoseius cetratus has short J2, Z1, Z2, and S1, S2 setae, not reaching the bases of following setae. Posterior half of dorsal shield with longitudinal garland of puncta between J and Z setae, peritremes extending anteriorly to midlevel of coxaⅡ. The genus Arctoseius and species Arctoseius cetratus are the first record in Korea. We provided the detail description of the species including the identification key in the family with some ecological notes.

• Eunsun Keum(Department of Bioresource Sciences, Graduate school, Andong National University)
• Mingu Kang(Gyeongsangbuk-do Agricultural Research and Extension Services)
• Chuleui Jung(Department of Bioresource Sciences, Graduate school, Andong National University) Corresponding author