Infestation of the woodwasp Tremex apicalis Matsumura (Hymenoptera, Siricidae) on the large-leaf dogwood Swida macrophylla (Wall.) with biological notes on its parasitoid wasps

The woodwasp Tremex apicalis ( Hymenoptera : Siricidae ) infesting a decayed stand of Swida macrophylla ( Cornales : Cornaceae ) was found in Honshu, Japan. Swida macrophylla was newly recorded as a host tree of the woodwasps. We observed oviposition behavior of Tremex apicalis on the tree trunk on May, 2015. In addition, prepupae and pupae of Tremex apicalis were observed in the wood on April, 2016. However, no larvae of Tremex apicalis were found at that time. This suggests that Tremex apicalis requires one year from egg to pupation. Parasitoid wasps, Ibalia japonica ( Hymenoptera : Ibaliidae ) and Megarhyssa spp. ( Hymenoptera : Ichneumonidae ), were also observed on the trunk (oviposition behavior of adult females) and in the wood (pupae and newly emerged adults). Because Ibalia and Megarhyssa are known as larval parasitoids of woodwasps and there were no other insect species in the wood, we conclude that these wasps are parasitoids of Tremex apicalis larvae. These parasitoids appear to be major natural enemies of Tremex apicalis larvae in the study site.