Two new species of Strepsiptera of the genus Xenos Rossi, 1793 (Xenidae) from the New World are described. Both are endoparasites of social wasps of the genus Mischonov., parasitizes Mischocyttarus navajo Bequaert, 1933, Mischocyttarus fl avitarsis (Saussure, 1854), and Mischocyttarus pallidipectus (Smith, 1857), whereas Xenos pallens Benda & Straka, sp. nov., is a parasite of Mischocyttarus costaricensis Richards, 1945 (Vespidae: Polistinae: Mischocyttarini).
Diagnoses and descriptions of female cephalothoraces are presented for all three species that parasitize species of Mischocyttarus. Diagnoses and descriptions of male cephalothecae are presented for Xenos bicolor sp. nov. and Xenos pallens sp. nov.
Additionally, a key for Xenos species parasitic on Mischocyttarus is provided based on characters of the female cephalothorax and male cephalotheca. Identifi cation of Xenos species based on external morphology is discussed.