The copulation process of a longicorn beetle, Psacothea hilaris consists of two successive events; frequent, short-time penis insertion (first stage) and a single long-time insertion (second stage). It was found that number of sperm stored in the Spermatheca decreased to about 2% of that of control females (which had mated only once), when the second males did first stage copulation without ejaculation. Second males discharged their rivals' sperm during first stage copulation. Scanning microscopic observations showed that the distal portion of the penis had a triangular process and pointed micro-bristles. Sperm displacement in this species is suggested by our observation of the removal of rival sperm by these characteristic structures on the penis.