Oxyrrhexis zephyrus sp.n., belong- ing to the Polysphincta genus-group, is described. Like all other species of this group, the new species is a koinobiont ectoparasitoid of spiders. It has been reared from the ground-living theridiid Enoplognatha serra- tosignata (L. Koch, 1879) in Norway. Chablisea shaanxiensis (Liu, He et Chen, 2009) comb.n. is pro- posed, ex Oxyrrhexis; thus Oxyrrhexis still comprises only four known species worldwide, but now with two species in the West Palaearctic. Oxyrrhexis carbon- ator (Gravenhorst, 1807), as its subspecies texana (Cres- son, 1870), is reported as new to the state of Alaska. Steatoda bipunctata (Linnaeus, 1758) is reported as the host of O. carbonator in Europe and, based on a large reared material from Finland, Sweden and Nor- way, this seems to be the only host of the nominate subspecies, at least in northern Europe. Parasitised hosts and the cocoons of the new species and O. carbonator are figured. The host record for the new species togeth- er with the data presented and discussed in this paper strongly support the hypothesis of Oxyrrhexis being a genus specialised in attacking the spider family Theri- diidae. Literature records of other spider families and non-spiders as hosts for O. carbonator are considered erroneous.