Title: Density-Related Changes in Male-Male Competitive Behavior in the Rice Brown Planthopper, Nilaparvata lugens (STAL) (Homoptera : Delphacidae)
Abstract: Male-male competition in Nilaparvata lugens (STAL) was experimentally investigated under laboratory conditions. The males were reared at three different unisexual densities (D1, D2 and D5) for 5 days after emergence before being used in the experiments. Three types of vibration signals (VS) named the calling signal (CS), the pre-aggressive signal (Pre-AS) and the aggressive signal (AS) were detected in the communication between a pair of males in D5. A barrier to visual and tactile stimuli between a pair had no marked influence on the communication through VS. Most single males emitted only CS, irrespective of the adult density. All of the D1 pairs communicated only through CS. The D5 pairs emitted AS more frequently than the D2 pairs. Rejection behavior (RB) by body shake was never observed in the D1 pairs. Distinct aggressive behavior, direct body attack (DBA), was observed only in the D5 pairs. Receptive conspecific females responded to the playback of CS by emitting the invitation signal (IS), but they did not so respond to the playback of Pre-AS and AS.