Abstract: 【Aim】 This study aims to evaluate the toxicity and ecological risk of neonicotinoid insecticides to Bombus terrestris workers so as to provide a scientific basis for application of neonicotinoid insecticides in greenhouse. 【Methods】 The acute oral and 
contact toxicities of eight neonicotinoid insecticides, including thiamethoxam, clothianidin, acetamiprid, imidacloprid, nitenpyram, dinotefuran, thiacloprid, and flupyradifurone, to adult workers of B. terrestris were tested by feeding and contact
methods, respectively, and the ecological risk of these neonicotinoid insecticides to B. terrestris was assessed. 【Results】 Clothianidin showed the highest toxicity to adult workers of B. terrestris by acute oral exposure, with the LD₅₀ values of 0.0433 and 0.0330 μg a.i./bee at 24 and 48 h after exposure, respectively, while fluorofuranone showed the lowest toxicity, with the LD₅₀ values of 72.4119 and 67.9079 μg a.i./bee at 24 and 48 h after exposure, respectively. The toxicities of the eight insecticides determined by acute contact were similar to those determined by acute oral exposure. Clothianidin showed the highest acute contact toxicity to adult workers of B. terrestris, with the LD₅₀ values of 0.0220 and 0.0192 μg a.i./bee at 24 and 48 h after acute contact, respectively, while fluorofuranone showed the lowest toxicity, with the LD₅₀ values of 141.7641 and 130.3062 μg a.i./bee at 24 and 48 h after acute contact, respectively. Ecological risk assessment revealed that acetamiprid, thiacloprid and flupirfenone showed low risk to adult workers of B. terrestris, while imidacloprid, nitenpyram and dinotefuran showed moderate risk. Thiamethoxam and clothianidin showed moderate risk to adult workers of B. terrestris in oral toxicity, while high risk in contact toxicity. 【Conclusion】 Among the eight neonicotinoid insecticides tested, acetamiprid, thiacloprid, and flupirfenone show low toxicity to adult workers of B. terrestris, while the other five neonicotinoid insecticides
(thiamethoxam, clothianidin, imidacloprid, nitenpyram and dinotefuran) show high toxicity. We recommend that the five neonicotinoid insecticides with high and moderate risk should be banned in order to avoid exposing bumblebees to insecticide risk, while the other three insecticides with low risk might be considered for application in the field.

Key words: Bombus terrestris, neonicotinoid insecticide, toxicity, risk assessment; facility agriculture