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Revision of the World species of Xeris Costa (Hymenoptera: Siricidae)
CJAI 28 -- September 25, 2015
doi: 10.3752/cjai.2015.28
Henri Goulet1, Caroline Boudreault1 and Nathen M. Schiff2

14. Xeris tropicalis Goulet

Fig. C14.1 (female habitus)

Xeris tropicalis Goulet, 2012: 267. Holotype female (CNC), labelled: [White] “6 mi.N.E. San Cristobal L. C., Chis. Mex. V.19 1969 H. E. Howden”, [White & black frame] “Xeris tarsalis (Cr.) D. R. Smith 75”, [Red] “HOLOTYPE Xeris tropicalis Goulet CNC No. 23908”. Type locality: Mexico, Chiapas, San Cristobal de las Casas. Specimen in perfect condition except left antenna broken and glued on label. Schiff et al., 2012: 267.

Xeris tarsalis; Smith, 1978: 89; Smith, 1988:243 (not Cresson, 1880: 52).

Diagnostic combination

Though only the female is known, we assumed that both sexes of X. tropicalis will be recognized by the broadly rounded and coarsely pitted transverse ridge dorsal to the mandible, the widespread and dense pits on the head dorsally, and the dense pits on the gena ventral to the genal ridge that are continuous with pits on the occiput.



Color. Head and thorax black except for white spot extending from dorsal edge of eye to surface between genal ridge and outer edge of eye (Figs. B2.17); antenna black but 7 apical flagellomeres reddish brown; last maxillary palpomere black. Pronotum in dorsal view with small white spot on anterolateral corner (Fig. C14.1). Legs black except sharply yellowish white at extreme apex of femora, basal 0.2 of tibiae, and base of tarsomere 1 (Figs. B2.23 and C14.1). Wings very darkly tinted except for clear basal 0.3 of hind wing, veins black or brown (including veins C, R and base of stigma on both sides of junction with vein 1r-rs) (Fig. C14.1 and as in Figs. B2.65). Abdomen black at base, but reddish brown after tergum 1.  Sheath with apical section black and basal section reddish brown.

Head. Distance between nearest edge of eye edgeand lateral ocellus edge 0.95 times as long as distance between inner edges of lateral ocelli (Fig. B2.19). Setae on frons and clypeus twice as long as diameter of a lateral ocellus (Figs. B2.17 and Fig. B2.27). Eye in lateral view (N = 1) with its maximum height 1.23 times as long as its maximum length (Fig. B2.17), and maximum height of eye 0.51 times as long as maximum height of head (from transverse ridge on gena above mandible to top of head) (Fig. B2.7). Gena in dorsal view with maximum distance between outer edges hardly wider than maximum width between outer edges of eyes (Fig. B2.2) (in frontal view, outer edges of eyes not intersecting genae, but very close to them less markedly so than in Figs. B2.5); in lateral view with distance between outer edge of eye and genal ridge 0.42 times as long as maximum length of eye (Fig. B2.17, measurements as in Figs. B2.77). Gena densely pitted ventral to genal ridge (Fig. B2.17), and with many very small to medium size pits (diameter of pit 0.05–0.3 times lateral ocellus diameter) between outer edge of eye and genal ridge (mainly near eye) (Fig. B2.17). Transverse ridge above mandible broadly rounded and coarsely pitted (Fis. B2.17, arrow). Vertex densely pitted and pits medium in size (diameter of pit 0.2–0.3 times lateral ocellus diameter), pits present on dorsoposterior edge of eye to occiput outside postocellar area, absent on small portion of postocellar area (Fig. B2.28)); pits dense, medium in size, and widespread along all very shallow gutter-like median furrow, a little more widespread near lateral ocelli (Fig. B2.28)).

Thorax. Pronotum in lateral view without polygonal pits on surface. Propleuron in lateral view with medium size polygonal pits on most of disc (as in Fig. C12.7); in ventral view with dense pits (hardly raised anteriorly) and a few smooth surfaces between pits with shallowly impressed meshes of microsculpture (Fig. B2.10). Transcutal furrow of mesonotum clearly outlined  and finely sculptured, thus mesoscutum and axilla clearly distinct (Fig. C14.2). 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 Fig. C12.6) abruptly curved away from wing edge; vein 3A reduced to a stump or absent.

Abdomen. Tergum 9 with meshes of microsculpture on ventral half below and above longitudinal furrow near center not well impressed and sculpticells clearly flat (slightly raised as scale above furrow) (as in Fig. B2.93, insert); median basin with base (outlined by two lateral black longitudinal furrows) 0.8 times as wide as its median length of basin, with maximum width of basin 1.7 times as wide as its median length, and basin 0.45 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) 0.85 times as wide as maximum width subapically; with large teeth in apical 0.3 (as in Fig.B2.110). Sheath. Basal section 0.4 times as long as apical section (N = 1) (Fig. B2.13); lateral surface of apical section with well-defined ridge (Fig. B2.13, insert); as long as fore wing length. Ovipositor. Lancet with 31 annuli (first 14 annuli outlined but difficult to see; N= 1); junction of basal and apical sections of sheath aligned between 4th and 5th annuli; major pits present on last 6 annuli before teeth annuli, and two preceding annuli with very small pits (as in Fig. C1.18).

MALE. Unknown

Taxonomic notes

At first sight the female of this species resembles that of X. tarsalis (Smith 1978), but upon close examination there are amazingly marked differences on the sheath and the ovipositor. We found additional structural differences on the pronotum and the propleuron sculpture, and color differences on in the legs and hind wing. In several characters (proportion between basal and apical sections of the sheath, between height of eye and height of head) this species represents an intermediate stage between X. tarsalis and the remaining species of Xeris. The female is unique in having numerous pits on the transverse ridge above the mandible and in leg color.

Host and phenology

The host of X. tropicalis is unknown but conifers are suspected. The single female was captured in mid-May.


Mexico: Chiapas. Xeris tropicalis is only known from the holoype, with the type locality in southernmost Mexico (see map C41.3 in Schiff et al. 2012).

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