Abstract: To investigate the insect community structure and ecological regulation potential in high-altitude small-seeded rape fields in Gannan Tibetan Autonomous Prefecture, this study conducted a systematic survey in June 2025 across six small-seeded rape fields representing different agricultural ecosystem types in Gannan. Species composition was recorded using transect walking surveys. Morphological identification and faunal analysis were employed to assess community structure and functional group division, while Jaccard similarity coefficients were used to analyze species similarity between different plots. The results showed that:(1) A total of 51 insect species belonging to 32 families and 9 orders were identified. Coleoptera(43.14%), Lepidoptera(21.57%), and Diptera(13.73%) were the dominant groups.(2) Phytophagous insects constituted the highest proportion within the functional groups, but many species exhibited dual ecological functions(e.g., adult Epicauta sibirica damages rape, while its larvae prey on pests).(3) The fauna was dominated by the Palearctic Realm(74.5%), significantly influenced by species dispersal from the North China and Central China subregions, with no strictly endemic Qinghai-Tibetan Plateau species found.(4) Jaccard similarity coefficients between plots ranged from 0.14 to 0.63. Plot 6 exhibited the highest uniqueness due to phenological differences. Plots 4 and 5 showed the highest similarity coefficient(0.63) and generally higher similarity with other plots(0.38—0.54), suggesting they may occupy a core position within the ecological network. In conclusion, the insect communities in Gannan rape fields exhibit high functional complexity and spatial heterogeneity. Based on the “top-down control” mechanism, two ecological regulation techniques are proposed:(1) Protecting native generalist and specialist natural enemies;(2) Utilizing ecological islands planted with functional plants to enhance natural enemy habitats.

Key words: plateau crop pests, faunal analysis, natural control, IPM