The Wharton Lab

Xenoschesis Foerster, 1869: 158. Type species: Exetastes fulvipes Gravenhorst, 1829. Included by Jemiller (1894: 147). Monobasic.

Homobia Foerster, 1869: 203. Type species: Colpotrochia cinctiventris Ashmead, 1896. Included by Davis (1897: 278). Monobasic. Synonymized by Cushman (1937: 244).

Glyptocentrus Kriechbaumer, 1894: 61. Type species: Exetastes fulvipes Gravenhorst, 1829. Monobasic. Isogenotypic with Xenoschesis Foerster, 1869.

The name Polycinetis is treated as a separate genus by Aubert (2000) but I see no reason to do so and have retained it as a subgenus following Townes (1970) and many others [including Yu et al. (2012)]. We have, however, placed the two subgenera on separate webpages.

Holarctic. There are seven valid species listed by Yu et al. (2012) for Xenoschesis s.s.

The two subgenera, Xenoschesis s.s. and Polycinetis, were separated by Townes (1970) on the basis of differences in propodeal sculpture and size of the ovipositor sheath. The propodeum has a more or less distinct petiolar area in Xenoschesis s.s. (Fig. 1) but not in Polycinetis (Fig. 2). The ovipositor and sheath are longer in Xenoschesis s.s. (Fig. 3) and the sheath is more bulbous in Polycinetis (Fig. 4).

Otherwise, Xenoschesis differs from other Ctenopelmatini by the shape of the apically pointed T8 in females and the more poorly developed propodeal carination.

Frons without median horn or elevated carina. Clypeus short and wide, ventral 0.25 distinctly impressed, with ventral margin sharp (though sometimes difficult to see as in Fig. 2), rounded margin above impression somewhat convex, sharp margin of impressed portion weakly concave; epistomal sulcus weak, clypeus not sharply separated from face. Malar space absent or present but short as in Fig. 2. Mandible (Fig. 2) moderately long, broad basally, weakly tapered and curving apically, ventral tooth about same size as dorsal tooth. Ocelli moderate to large, lateral ocellus varying from slightly shorter than distance between ocellus and eye to equal this distance and at least in some males, diameter of lateral ocellus greater than distance to eye. Maxillary palp distinctly shorter than head height in some species, about equal to head height in others; female antenna a little shorter than length of body; first flagellomere without tyloid. Hypostomal carina joining occipital carina well above base of mandible; occipital carina complete. Epomia present though sometimes weak. Dorsal end of epicnemial carina distinctly separated from anterior margin of mesopleuron. Notaulus deep, narrow, varying in length from half distance to tegula to slightly posteriorad tegula, then abruptly ending: not extending full length of mesoscutum. Distinct u-shaped notch between anterior end of lateral longitudinal carina of propodeum and adjacent part of metanotum usually distinctly visible in lateral view; metanotum overhanging propodeum medially in lateral view, but not forming a distinct u- or v-shaped notch; pleural carina usually present only dorsally, represented ventrally by a deep sulcus; propodeal carinae reduced: lateral longitudinal carinae of propodeum always present but incomplete and usually weak, petiolar area (Fig. 3) margined laterally by portions of median longitudinal carinae, weakly closed anteriorly by wrinkled sculpture or weak carina; areola absent as are other carinae. Apical margin of mid tibia expanded as an angular tooth not quite so protruding as that on fore tibia; comb on hind tibia not well developed; hind tibial spurs fairly long, slender (Fig. 1); membranous flap on apical margin of fore tibia present; all tarsal claws simple for most of their length, with a few, short pectinations basally, these hard to see (Fig. 4). Fore wing areolet usually present (Fig. 1). Hind wing with first abscissa of CU1 varying from approximately equal in length to 1cu-a to distinctly shorter than 1 cu-a. T1 long and relatively slender basally, gradually widening posteriorly, apex about 3 (female) times wider than near base; dorsal carinae sharp basally, rounded and less distinct posteriorad spiracle though often extending to apex as low, rounded ridges, with distinct but shallow basal depression at dorsal tendon attachment; dorsal-lateral carina sharp and distinct from spiracle to apex; glymma absent. S1 extending about 0.8 times distance to spiracle. T2 lateral carina rounded, often indistinct; T2 thyridium absent; laterotergites of T2 and T3 completely separated by creases. Ovipositor and sheath (Figs 6, 7), straight, distinctly protruding from apex of metasoma, ovipositor with broad subapical, dorsal notch. cerci and anal opening completely encircled by 8th metasomal tergum, the tergum pointed apically (Fig. 6). Apex of female metasoma as in Fig. 6.

A detailed biology of X. fulvipes (Gravenhorst) attacking Cephalcia is provided by Eichhorn (1988). The following hosts and references for those hosts records are taken from Yu et al. (2005).

Acantholyda erythrocephala Pinus (Aubert 2000)
Acantholyda hieroglyphica (Ozols 1961)
Acantholyda posticalis (Hardtl 1943; Aubert 2000)
Acantholyda posticalis Pinus (Shaw et al. 2003)
Cephalcia abietis (Sedivy 1965, Sedivy 1967; Jahn 1978; Eichhorn 1988; Martinek 1990; Kanecka 1993, 1995)
Cephalcia alpina (Rohrig 1953)
Cephalcia arvensis (Boas 1933; Martinek 1991)
Pamphilius depressus (Hinz 1961)
Pamphilius gyllenhalli (Ozols 1961)
Pamphilius hortorum (Hinz 1961)
Pamphilius hypotrophicus (Strand 1915; Scheidter 1916; Schimitschek 1964)

The following host records are doubtful.

Tenthredo campestris (Ratzeburg 1844)
Thaumetopoea pityocampa (Romanyk and Ruperez 1960)
Trichiosoma sorbi (Ozols 1961)

This page was assembled by Bob Wharton as part of a larger collaborative effort on the genera of Ctenopelmatinae, with work on the Ctenopelmatini assisted by Matt Clark. Page last updated April, 2015.
This work would not have been possible without the groundwork provided by Ian Gauld’s study of the Australian and Costa Rican faunas, and we are particularly grateful for his assistance in many aspects of this study. We also thank the following curators for extended loans of the material used for this study: David Wahl of the American Entomological Institute and Andy Bennett of the Canadian National Collection. We also thank David Wahl for useful feedback throughout our study and Dave Karlsson for making available material from the Swedish Malaise Trap Survey (Trap ID 58, Collection event 207). Matt Yoder provided considerable assistance with databasing issues, and our use of PURLs (http://purl.oclc.org) in this regard follows the example of their use in publications by Norm Johnson. Heather Cummins, Matt Clark, Patricia Mullins, Caitlin Nessner, Amy James, and Cheryl Hyde graciously assisted us with image processing, formatting, and literature retrieval. This study was supported by the National Science Foundation’s PEET program under Grant No. DEB 0328922 and associated REU supplement nos DEB 0723663, 0822676, and 0923134.
This material is based upon work at Texas A&M University supported by the National Science Foundation under Grant Number DEB 0328922 with REU supplements DEB 0723663, 0822676, and 0923134. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.