Description and biological notes of the first species of Xenos (Strepsiptera: Stylopidae) parasitic in Polistes carnifex F. (Hymenoptera: Vespidae) in Mexico Kathirithamby, Jeyaraney Hughes, David P. Zootaxa 2006 1104 35 45 Kathirithamby and Hughes Kathirithamby and Hughes [264,817,1537,1563] Insecta Xeninae Xenos Animalia Strepsiptera 3 38 Arthropoda species hamiltoni sp. nov.    Type. Holotypeɗ: MEXICO, Estación de Biología “Los Tuxtlas” UNAM, 8 May 2002, (D. Hughes) (Colección Nacional de Insectos, Instituto de Biologia, Universidad Nacional Autonoma de Mexico, MexicoCity).  Paratypes. ɗ: MEXICO, Estación de Biologia “Los Tuxtlas” UNAM, 8 May 2002, (D. P. Hughes) (Colección Nacional de Insectos, Instituto de Biologia, Universidad Nacional Autonoma de Mexico, MexicoCity). ɗ: (same data as above), (D. P. Hughes) (Colección Nacional de Insectos, Instituto de Biologia, Universidad Nacional Autonoma de Mexico, as long as pro­ and mesothorax (scutum length, 0.32–0.35mm). Scutellum length: 0.42–0.45 mm. Postlumbium half the length of scutellum (length, 0.25–0.27 mm). Postnotum: twice as long as scutellum (length, 0.80–0.81 mm) ( Fig 3A).   FIGURE 2.  Xenos hamiltoni sp. n.SEM of lateral view of head. Scale bar=0.1 mm. Wing: R1 is infuscated and interrupted in the middle; R2 arises a little after this and is as long as R3, R4 not reaching margin, R5 is short and arises below R4, MA, CuA1, CuA2 and CuP present and uninterrupted. Length of wing (along its longest length) = 2.77–2.83 mm( Fig 3C). Length of IX th abdominal segment, 0.25–0.26 mm(Fig 1D). Length of adeagus, 0.24–0.27 mm( Fig 3B). Male cephalotheca. Length, 0.86–0.88 mm; width, 1.11–1.3 mm. The male cephalothecae extruded both between abdominal tergites and sternites (II–III, or III–IV or IV–V) ( Table 1).   Diagnosis. This is the nineteenth species of  Xenosto be described from Mesoamerica and the first from Mexico. The new species is distinguished by short, pointed maxillary palpi which fits in a socket of the basal segment. The aedeagus, with pointed anterior and posterior heads and a hump on the dorsal posterior region, and the lengths of the pro­and mesothorax, are more than a third of the length of the metathorax.   FIGURE 3.  Xenos hamiltoni sp. n.A. Dorsal view of head and thorax. Scale bar=0.5mm. B. Aedeagus. Scale bar = 0.2 mm. C. Wing (right). Scale bar = 1.2mm.   TABLE 1: Position of the extruded male pupae of  Xenos hamiltoni sp. n.in the abdomen of the wasp  Polistes carnifexF.    Number of male pupae Position on abdomen of  Polistes  1 IInd & IIIrd tergites  2 IIIrd & IVth tergites  2 IVth & Vth tergites  1 IVth & Vth sternites  2 IIIrd & IVth sternites The new species can be distinguished from  X. zikaniwhich has no basal maxilla segment, a long palpus which is 1/8 shorter than mandibles (  X. hamiltonihas a long basal segment and very short palpus), R3 arising close to R4 and R5 is absent in the wing (R3 not arising close to R4 and R5 present in  X. hamiltoni) and hump on dorsal posterior of aedeagus absent.   Etymology.The new species is named after the late Bill Hamilton FRS, who inspired us to study the behavioural ecology of the Strepsipterafamily Stylopidae.