Abstract: Most mirid bugs are phytophagous. As a common insect group in grasslands, it is an important component of biodiversity. From the end of June to the beginning of September in both 2017 and 2018, we investigated the diversity and distribution of mirid bugs by sweeping net method, with the aim to provide basic data for further research. A total of 1825 individuals were collected, belonging to 65 species and 34 genera. Among them, 858 individuals (34 species, 20 genera) were from Horqin grassland and 967 individuals (52 species, 27 genera) from Hulunbuir grassland. Apolygus spinolae, Trigonotylus caelestialium,and Europiella artemisiae were dominant species in Horqin grassland, while Adelphocoris lineolatus, Lygus gemellatusandPolymerus cognatus were the dominant species in Hulunbuir grassland. The Margalef richness index (7.42), Shannon index (3.04), and Simpson diversity index (0.93) of mirid bugs were higher in Hulunbuir grassland, whereas Pielou evenness index (0.77) was higher in Horqin grassland. The genera and species richness in subfamily Mirinae was obviously higher in the Hulunbuir grassland, though the difference in abundance between the two grasslands was not significant. There was no obvious difference between the two grasslands in the abundance and number of genera and species in subfamily Orthotylinae. The subfamily Phylinae had higher number of genera and species, and abundance in Horqin grassland. The similarity coefficient of mirid bug species between the two grasslands was 0.32. It was concluded that the diversity of mirid bugs in Hulunbuir grassland was higher than that in Horqin grassland, and that species compositions were moderately dissimilar between the two grasslands.

Key words: mirid bug, diversity, similarity analysis, Horqin grassland, Hulunbuir grassland.