Abstract: In order to clarify the species and parasitic morphology of the parasitic natural enemy insect-parasitoid flies of the grassland caterpillars, three species of parasitoid flies hatched from the grassland caterpillar were identified in this study by morphological classification and molecular sequencing: Gymnophryxe inconspicua (Villeneuve, 1924), Exorista laruarum (Linnaeus, 1758) and Chetogena gynmephorae Chao et Shi, 1987. Among them, the dominant species of parasitic natural enemies of grassland caterpillars in this area are Gymnophryxe inconspicua and Exonista laruarum. Through the survey and statistics of the parasitism rate of natural enemies in grassland caterpillars, the parasitism rate of parasitoids in grassland caterpillars was found to be increasing and then decreasing, and the parasitoid flies mainly parasitized the 6^th and 7^th instar larvae of grassland caterpillars from July to August. In this experiment, indoor dissection revealed that a single prairie caterpillar hosted from 2 to 5 parasitoid larvae. The purpose of this study is to lay a foundation for the biological control technology of grassland caterpillars, and also to provide a theoretical basis for the parasitism mode, parasitism period and parasitism state of parasitic natural enemy insects, which is of great significance for the protection of the ecological environment of grassland in alpine rangeland of the Qinghai-Tibet Plateau.

Key words: Gynaephora qinghaiensis, natural enemy tachinids, species identification, parasitism