Presence of allochronic populations of the white grub beetle Dasylepida ishigakiensis (Coleoptera: Scarabaeidae) on Ishigaki Island, Japan

To investigate the seasonal prevalence of Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scarabaeidae), synthetic sex pheromone traps were placed on Ishigaki Island in 2008 and 2009. One population is known to occur in the forest and fly for mating from early March to early April. The trap data revealed a second population in the farmland that flew for mating much earlier (mid-January to late February) than did the other population, indicating the presence of allochronic populations. Adults of the farmland population were caught throughout the sugarcane-grown area on the island, whereas those of the forest population appeared to be limited to the forest area. The temporal pattern of trap catches of each population was generally the same between 2008 and 2009. Relatively large trap catches were observed in the west central plane area and a small northern area of the northeastern peninsula of the island. These results suggest that, although it has not caused any damage to agricultural crops on this island, this beetle might be a potentially serious pest of sugarcane crops in the future, as reported on another island of Okinawa.