Fig. C16.1 (female habitus)
Holotype. Female (OLML), in good condition except last eight flagellomeres on the right and apical section of right sheath glued on point, and last four flagellomeres on the left missing, labelled [White] “China, Yunnan, 2, 5-3, 8km 27,20N; 100, 11E Habashan mts. SE slope 3.-6. 6. Lgt. S.Becvar, 1995”; [Red] “HOLOTYPE Xeris xanthoceros ♀ H. Goulet, 2015”.
Among specimens with a light yellow fore wing cell C cell and with short setae on the head [xanthoceros, malaisei, pallicoxae, spectrum, and xylocola], X. xanthoceros is recognized in the female and probably the male by the narrow shiny surface medially on the pronotum dorsally and the more restricted coarse pits on the lateral surface of the pronotum, and in the female by the light reddish-brown flagellum beyond flagellomere 4 and by the black pronotum.
Color. Head black except for white spot (rarely missing) on gena dorsal to middle of eye; white spot not clearly outlined and ventral edge not extending to genal ridge (Fig. B2.139); scape and pedicel light reddish brown ventrally and brown dorsally, flagellomere 1–3 brown and following flagellomeres light reddish brown; last maxillary palpomere reddish brown (Fig. B2.117). Thorax black except for yellowish-white band on pronotum along margin and below anterolateral corner (Fig. B2.143). Legs beyond coxae light reddish brown; coxae black (Fig. C16.1). Fore wing clear except for lightly tinted band in apical 0.25, and near junction of veins CU and 2 cu-a (as in Fig. B2.67); costal cell very light yellow (paler in old specimens) (as in Fig. B2.40); most of area ventral to anal cells yellowish brown; veins black but white at base of stigma on both sides of junction with vein 1r-rs (as in Fig. B2.40). Sheath with apical section black and basal section reddish brown.
Head. Distance between nearest eye edge and lateral ocellus edge about 1.3 times as long as distance between inner edges of lateral ocelli (as in Fig. B2.20). Setae on clypeus 0.6–0.7 as long as length of lateral ocellus (Fig. B2.139). Eye in lateral view (N = 1) with its maximum height 1.4 times as long as its maximum length (Fig. B2.139), and maximum height of eye 0.53 times as long as maximum height of head (from transverse ridge on gena above mandible to top of head) (Fig. B2.139), measurements as in Fig. B2.8). Gena in dorsal view with maximum distance between outer edges a little wider than maximum distance between outer edges of eyes (as in Fig. B2.43) (in frontal view outer edges of eyes clearly not intersecting genae) (as in Fig. B2.5); in lateral view with distance between outer edge of eye and genal ridge 0.45 times as long as maximum length of eye (Fig. 2.139), measurements as in Fig. B2.77), with few or no pits ventral to genal ridge, and with small to moderate size pits (diameter of pit 0.1–0.2 times lateral ocellus diameter) between outer edge of eye and genal ridge (mainly near eye) (Fig. B2.139). Transverse ridge above mandible narrow, sharp and mainly smooth (Fig. B2.139). Vertex scarcely pitted and pits medium in size (diameter of pits 0.2–0.3 times lateral ocellus diameter), pits present from dorsoposterior edge of eye to occiput outside postocellar area, absent on most of postocellar area, pits dense and medium in size along all of shallowly outlined and gutter-like median furrow but a little more widespread near lateral ocelli (as in Fig. B2.43).
Thorax. Pronotum in dorsal view along yellowish-white longitudinal band with irregular ridges between large teeth ( as in Fig. B2.95) and with a narrow parallel shiny surface medially, the surface without impression (Fig. B2.135); in lateral view with coarse polygonal pits on 0.3–0.7 of posterior surface (as in Fig. B2.97). Propleuron in lateral view with small polygonal pits over most of surface (as in Fig. C12.7); in ventral view generally with dense small teeth often forming coarse polygonal pits with smooth or shallowly meshed surface in between (as in Fig. B2.22). Transcutal furrow of mesonotum obscured by coarse pits, thus mesoscutum and axilla apparently fused (Fig. C16.3). Metanotum with surface posterior to cenchrus and lateral 0.5 of metascutellum coarsely pitted (pit 0.1–1.5 times as wide as diameter of lateral ocellus) (as in Fig. B2.105). Fore wing in middle 0.3 of vein 2A diverging considerably (as in Fig. C12.6) away from wing edge and then less (as in as in ) abruptly curved away from wing edge; vein 3A reduced to a stump (N = 1).Abdomen. Tergum 8 on central area with deeply pitted sculpticells forming transverse lines of various lengths (Fig. C16.4), and lateral margin not shiny (Fig. B2.141, insert). Tergum 9 with meshes of microsculpture on ventral half below longitudinal furrow near center clearly impressed and sculpticells flat, meshes above longitudinal furrow near center well impressed and sculpticells scale-like (as in Fig. B2.92, insert); median basin with base (outlined by two lateral black longitudinal furrows; N = 1) 0.9 times as wide as its median length, with maximum width of basin 1.4 times as wide as its median length and basin 0.57 times as long medially as median length of cornus (measurements as in Fig. A3.2). Cornus constricted in dorsal view, its minimum width (at constriction) about 0.8 times as wide as maximum width subapically (as in Fig. C1.15); with large teeth in apical 0.3 (as in Fig. B2.110). Sheath. Basal section 0.30 times as long as apical section (N = 1) (Fig. C16.1); lateral surface of apical section with well-defined ridge (as in Fig. B2.13, insert); length 1.4 times as long as fore wing length. Ovipositor. Lancet with 28 annuli (first 5 annuli hard to see, but still outlined; N = 1); junction of basal and apical sections of sheath aligned between 3rd and 4th annuli; major pits present on last 8 apical annuli before teeth annuli, and with a small pit on each of the annuli 2–6 annuli and a very small pit on each of the annuli 7–19 (Fig. C16.2).
Xeris xanthoceros is related to species of the X. spectrum lineage based on the presence of a pit on each of the most basal annuli. It is also similar to females of X. xylocola and X. malaisei because of their partially light reddish-brown flagellum. It is closest to X. xylocola because of the narrow shiny median surface of the pronotum in dorsal view. The two species are segregated on color pattern and structure.
The specific name “xanthoceros”, a noun, means “yellow horn” referring to the mainly light reddish-brown flagellum of the female.
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