Woodwasps (Hymenoptera: Siricidae) are saproxylic insects and a common forest pest. Siricid woodwasps are classified into two subfamilies: Siricinae and Tremecinae. All known symbiotic fungi of Siricinae are in the genusAmylostereumBoidin while some species of Tremecinae have been observed to have a relationship with the fungusCerrenaunicolor(Bull.) Murrill. Previous studies about the host searching behavior of woodwasps and their parasitoids have focused primarily on the subfamily Siricinae.We analyzed the role ofC.unicolorvolatiles on the host searching behavior ofTremexapicalisMatsumura (Hymenoptera: Siricidae: Tremecinae) and its parasitoid Ibalia (Tremibalia) japonica Matsumura (Hymenoptera: Ibaliidae). The results of an olfactory response experiment indicated that the females ofT.apicalisand its parasitoid find their respective hosts using volatiles fromC.unicolor. Using DNA barcode, we identified basidiocarps on the trees infested withT.apicalis.The basidiocarps were all white-rot fungi that cause sapwood decay, includingC.unicolor. Two additional species that we identified belonged to genera closely related toC.unicolor.Woodwasp species are known to carry symbiotic fungi in a pair of specialized sacs called mycangia. Notably we found that mycangia-like structures were absent in the abdomens ofT.apicalisfemales. To the best of our knowledge,Xerisspectrum(Linnaeus) (Hymenoptera: Siricidae) is the only reported example of woodwasp species that do not contain symbiotic fungi in their bodies.Our results suggested that: (1)T.apicalisfemales search for host wood that is already infected with sapwood decaying fungus using volatile compounds; (2)T.apicalis’ female parasitoid also uses volatile compounds from fungus to locate wood that is infested with its potential host.