New aspects of the biology of Melanesian rhinoceros beetle Scapanes australis (Col., Dynastidae) and evidence for field attraction to males

Scapanes australis is a major coconut pest, endemic in Papua New Guinea. Early in the night, males placed singly into artificial galleries made in young coconut palms exhibited a sex-specific calling behaviour for 1 to 1.5 h. Coming to the gallery entrance, they raised the abdomen and the hind legs, the head lowered inside the gallery, and emitted a liquid secretion, rhythmically smeared by crossing the legs. Females, which did not behave so, were very mobile. The adult flying period coincided with the male calling behaviour. In field assays with caged insects on coconut palms, attraction of both sexes to males was evidenced when they were calling. Males fought for gallery possession at a male arrival. No aggression but mating was observed with arriving females, which proved not to have developed oocytes. The strong male attraction was confirmed using automatic traps, baited with one live male in a sugarcane piece. Males were assumed to release an aggregation pheromone. Further studies are underway to identify the putative pheromone. (Résumé d'auteur