Ecological Traits of Three Species of Xiphydria Woodwasps from Japan: Host Tree Species and Eggs, Symbiotic Fungi, and Mucus in Their Bodies

Woodwasps (Siricidae and Xiphydriidae) inhabit living, weakened, or freshly dead trees and their larvae feed on sapwood. Siricidae have been intensively researched for pest management. In contrast, the ecology of Xiphydriidae remains largely unknown. In the present study, we collected xiphydriid woodwasp adults and dissected female adults to elucidate the cornerstone ecology of this family and compared these findings with those of siricid woodwasps. The findings provide new host records for these species and indicate that their host ranges span multiple families. Notably, all Xiphydria species had female-biased sex ratios. All adult females had gourd-shaped eggs, similar to those found in gall wasps (Cynipidae), which contrast with the oval-shaped eggs of Siricidae. Slit-like mycangia were located at the base of the ovipositor, with pairs of fungal masses composed of hyphal fragments or spores directly positioned below the seventh sternum, differing structurally from the pouch-like mycangia in Siricidae. Mucus reservoirs and secretory glands were found in the terminal abdominal segments, similar to Siricidae. Mucus in X. annulitibia and X. ogasawarai was colorless and transparent, as reported in Siricidae, whereas X. eborata exhibited deep wine-red mucus, which is the world’s first discovery in all dissected species of Siricidae and Xiphydriidae.