Revision of the world species of Xeris Costa (Hymenoptera: Siricidae)
Xeris is one of ten extant genera of Siricidae known as as woodwasps or horntails. They are important wood-boring Hymenoptera from the Northern Hemisphere. Adults and larvae of Xeris are often intercepted at ports and are consequently of concern as potential alien invasive species. The genus consists of 16 species with eight in the New World and eight in the Old World. Despite records of numerous intercepted specimens, no species has been accidentally established anywhere. Five new species all by Goulet are described: Xeris degrooti n. sp., X. pallicoxae n. sp, X. umbra n. sp., X. xanthoceros, n. sp and X. xylocola n. sp. Two new synonyms are proposed: Neoxeris melanocephala Saini and Singh, 1987 = X. himalayensis Bradley, 1934 and X. ndianus Vasu and Saini, 1999 = X. himalayensis Bradley, 1934. Two synonyms are upheld:Sirex nanus O. F. Müller, 1776 = X. spectrum (Linnaeus, 1758) and Sirex emarginatus Fabricius, 1793 = X. spectrum (Linnaeus, 1758). Two changes in rank from subspecies to species level are proposed: X. cobosi Viedma and Suarez from X. spectrum cobosi and X. malaisei Maa from X. spectrum malaisei. We characterize the genus, the world species are keyed and a partial reconstructed phylogeny is proposed. For each species we include the following (if available and/or pertinent): synonymic list, type material, diagnosis, description of one or both sexes, origin of specific name, geographical variation, taxonomic notes, biological notes, hosts and phenology (emergence or flight period data), and range. DNA barcoding (cytochrome oxidase 1 – CO1) was shown to be a reliable identification tool for adult and larval Siricidae (Schiff et al. 2012). Larvae cannot be identified using classical morphological methods, but DNA barcoding can accurately distinguish larvae of Xeris spp. We include barcodes for nine of the 16 species (one species, X. pallicoxae, could be a complex of two species based on barcodes). DNA data has been most useful for confirming morphologically similar species, associating specimens with discrete color forms, and deciding the rank of populations. The results have proved to be accurate and in agreement with almost all species determined by classical morphological methods.