Abstract
Predation of Trogossita japonica Reitter (Coleoptera: Trogossitidae) on the Japanese pine sawyer, Monochamus alternatus Hope (Coleoptera: Cerambycidae), the vector of pine wilt disease, was investigated by release of adults of both species into cages containing pine bolts. In an experiment held in 1996, both species were released simultaneously for two weeks in July. After the release period, most cerambycid beetles released with the predators were still alive and any dead beetles had no external wounds. Thus, it was clear that the predator was not able to predate on the adult of the cerambycid beetle in the field, and the predators were thought to have starved during the release period and so laid few eggs. In a similar experiment held in 1997, final instar larvae of M. alternatus were pinned on bolts as diet for the predators. Ovarial development showed that the female predators laid eggs. Bolts were then investigated further by cutting them open, and the number of cerambycid beetles in bolts did not differ from that of the control in which predators were not released. These results show that there was no observed effect of predation of larval offspring of released predators on larval offspring of released cerambycid beetles. Three larvae of the predator, however, were collected from outdoor cages where all bolts were heavily attacked by bark beetles but only one from indoor cages where only M. alternatus was present and where no bark beetles had attacked bolts. These results indicate that bolts containing various other invertebates may support the development of the predator and increase its predatory effect.
