Abstract: 【Aim】The parasitic beetle, Dastarcus helophoroides (Fairmaire) is the dominant species among the natural enemies against the wood-boring insects of trees. The research of the circadian rhythm of male and female adult behaviors of D. helophoroides can help us to understand their biological characteristics and illustrate their living habits. 【Methods】 The behaviors of D. helophoroides adults were observed and recorded at a 30 min interval by single rearing separately under the temperature 27±1℃ and relative humidity 65%±10% in the laboratory from July 10th to 15th, 2014. The observed behaviors of males and females were divided into five types, i.e., moving, foraging, drinking, resting with contacting wood and resting without contacting wood. 【Results】 The moving and resting with contacting wood behaviors of D. helophoroides adults showed obvious circadian rhythm. The moving behavior mostly took place during the dark period, and the peak of moving was recorded at 20:30-22:30 and 2:00-4:00 of the dark period, while the lowest was recorded at 6:00-16:30 of the light period. The resting with contacting wood occurred mainly at 9:30-16:30 of the light period and 0:00-1:30 of the dark period, while the lowest was recorded at 20:30-23:00 of the dark period. The occurrence of foraging and drinking behavior was very low within a day and happened mainly after 0:00 and before 14:00 o’clock. The peak of resting without contacting wood behavior was recorded at 0:30-3:30 and 20:00-22:00 of the dark period. The percentages and time points of occurrence of various behaviors showed no significant difference between females and males. 【Conclusion】 The behaviors of D. helophoroides are influenced significantly by light and dark conditions. The moving behavior mostly takes place during the dark period; however, there is no significant difference in the percentages of various behaviors between females and males.

Key words: Dastarcus helophoroides, adult, sexual difference, activity behavior, circadian rhythm