Abstract: 【Aim】 This study aims to provide data for elucidating the application value of the body temperature of the diamondback moth, Plutella xylostella, in its management. 【Methods】 At different temperatures in the artificial climate incubators (ambient temperatures), the body temperature of the 2nd, 3rd, and 4th instar larvae of P. xylostella was measured, and the relation equations between the body temperature of various instar larvae (y) and the ambient temperature (x) were established. Meanwhile, the body temperatures of the 3rd instar larvae of P. xylostella at different time after treatment with different concentrations of avermectin, chlorpyrifos, fipronil and cypermethrin, respectively, at different ambient temperatures were measured. 【Results】 The relation equations between the ambient temperature (x) and the body temperature (y) of the 2nd, 3rd and 4th instar larvae of P. xylostella were y＝0.95x+1.19 (r=0.9463), y＝0.95x+1.18 (r=0.9988), and y＝0.93x+1.45 (r=0.9989) with the corresponding isothermal points of 22.16℃, 21.40℃ and 21.41℃, respectively. When the ambient temperature was set at 15℃ or 40℃, none of the four pesticides changed the body temperature of the 3rd instar larvae of P. xylostella. However, at the other ambient temperatures, the body temperature of the 3rd instar larvae of P. xylostella could be changed by pesticide treatment. For avermectin, at 25℃, the body temperatures of the 3rd instar larvae in the 2, 4 and 8 mg/L treatment groups at 12 h, 2 and 4 mg/L treatment groups at 24 h, 0.5, 2, 4 and 8 mg/L treatment groups at 36 h and 0.5, 1, 2 and 8 mg/L treatment groups at 48 h were significantly increased, while that in the 8 mg/L treatment group at 24 h was significantly decreased; at 30℃, those in the 0.5 mg/L treatment group at 24 h and 1 mg/L treatment group at 36 h were significantly decreased and those in the 1 mg/L treatment group at 48 h and the treatment groups at various concentrations at 60 h were significantly increased; and at 35℃, only those in the 1 and 8 mg/L treatment groups at 48 h were significantly decreased as compared to that in the control. For chlorpyrifos, at 20℃, the body temperatures of the 3rd instar larvae in the 50, 200 and 800 mg/L treatment groups at 24 h and 100, 400 and 800 mg/L treatment groups at 36 h were significantly decreased; at 25℃, those in the 100 and 200 mg/L treatment groups at 12 h, 800 mg/L treatment group at 24 h and 100, 200 and 800 mg/L treatment groups at 60 h were significantly decreased, but those in the 50, 100, 200 and 400 mg/L treatment groups at 24 h, 100 and 200 mg/L treatment groups at 36 h and 100 and 400 mg/L treatment groups at 48 h were significantly increased; and at 30℃, only that in the 800 mg/L treatment group at 24 h was significantly decreased and those in the 50, 100, 200 and 800 mg/L treatment groups at 60 h were significantly increased as compared to that in the control. For fipronil, at 20℃, only the body temperature of the 3rd instar larvae in the 0.5 mg/L treatment group at 36 h was significantly decreased; at 25℃, that in the 4 
mg/L treatment group at 12 h and those in the treatment groups at various concentrations at 60 h were significantly decreased, and that in the 0.5 mg/L treatment group at 24 h and those in the 0.25, 1 and 2 mg/L treatment groups at 48 h were significantly increased; at 30℃, those in the 0.25 and 0.5 mg/L treatment groups at 12 h, 0.25 and 2 mg/L treatment groups at 24 h, 4 mg/L treatment group at 48 h and 2 mg/L treatment group at 60 h were significantly decreased; and at 35℃, only those in the 0.25 and 0.5 mg/L treatment groups at 60 h were significantly increased as compared to that in the control. For cypermethrin, at 20℃, the body temperatures of the 3rd instar larvae in the 2 and 8 g/L treatment groups at 36 h and 4 and 8 g/L treatment groups at 48 h were significantly increased; at 25℃, those in the 2, 4 and 8 g/L treatment groups at 12 h were significantly decreased and those in the 0.5, 4, and 8 g/L treatment groups at 24 h, 1, 4 and 8 g/L treatment groups at 36 h, and 1, 2 and 4 g/L treatment groups at 60 h were significantly increased; and at 30℃, those in the 0.5 and 1 g/L treatment groups at 12 h, 0.5, 1, 4 and 8 g/L treatment groups at 24 h and 1, 2 and 8 g/L treatment groups at 60 h were significantly decreased as compared to that in the control. 【Conclusion】 The autonomic thermoregulation ability of P. xylostella larvae is comparatively low. Avermectin, chlorpyrifos, fipronil or cypermethrin treatment can affect the body temperature of the 3rd instar larvae of P. xylostella, but the effect varies with the pesticide type and concentration, ambient temperature and treatment time. The results expand the studies on pesticide toxicology and pest control.

Key words: Plutella xylostella, body temperature, isothermal point, pesticides, toxicity