The Mesostigmata are a great diversity of invertebrate parasite-phoretic of insects, and free-living predators in terristerial ecosystem. The Ascidae are an important group of predator that inhabit various microhabitats such as leaf litter, rotten wood, anthills and bird’s nests. Their role in those habitats is imprtant and they can be used as biological indicator and as well as biological control agent. We collected mites from sciarid fly in mushroom. The genus Arctoseius and Arctoseius cetratus were recorded for first time in Korea. We also described the habitats and identification keys to the species. 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 mid-level of coxaⅡ.

• Eunsun Keum(School of Bioresource Sciences, Andong National University, Andong 760-749, Republic of Korea)
• Chuleui Jung(School of Bioresource Sciences, Andong National University, Andong 760-749, Republic of Korea)