To ascertain the mating behavior of the sugi bark borer, Semanotus japonicus, adults were released at varying densities on live standing Japanese cedars in a wood, and their mate searching behavior, mounting behavior, and copulation were observed continuously for 24 hr individually. Mate encounters occurred mainly between actively-searching males and ovipositing females, resting females and/or walking females, but in rarer cases, between resting males and walking females. Even at lower

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... , individuals encountered mates more than once in 24 hr of observation. Coupled pairs were sometimes interfered with a third individual at higher densities. Seventy-six percent of mounting behavior continued for less than 10min and 82% of copulation was for less than 5min. Mating occurred mostly between dusk and dawn. Adults of both sexes mounted and copulated repeatedly, both with single mates and several mates. Two types of fighting were observed between males: fighting between unpaired males, and fighting between an unpaired male and a paired male. The frequency and intensity of the fighting were higher and stronger in the latter case than the former.