Diel emergence and dispersal rhythms in the bamboo borer Dinoderus minutus (Coleoptera: Bostrichidae).

Biological rhythms regulate insect activity and represent a conserved adaptive trait across life forms. Understanding the behavioral rhythms of dispersive cryptic species is important for elucidating their ecological interactions and improving pest management strategies. In this study, we investigated the diel patterns of emergence and flight activity of the bamboo borer Dinoderus minutus under field and laboratory conditions using a chronobiological approach. Field emergence was evaluated using emergence cages containing naturally infested bamboo culms, whereas flight activity was monitored using semiochemical-baited cross-vane panel traps. In laboratory assays, locomotor and flight activities were compared between morning and afternoon periods. Periodicity analyses revealed significant daily rhythms in both emergence and flight activity. Cosinor analyses indicated that most individuals emerged around 14:00 h and initiated flight shortly thereafter, at around 16:00 h, which corresponded to the acrophase of each behavior. No emergence or dispersal activity was recorded during the night period, indicating strictly diurnal dispersal behavior. Laboratory experiments corroborated field observations, showing significantly greater flight initiation, locomotor activity, velocity, and distance traveled during the mid-afternoon than in the morning. These results demonstrate that D. minutus exhibits a predictable behavioral periodicity, with peak emergence and flight activity concentrated during the mid-afternoon. This information provides an important basis for field monitoring, detection, and the development of pest management strategies targeting bamboo borer populations.