Xenos bicolor Benda & Straka, 2022

Benda, Daniel, Pohl, Hans, Beutel, Rolf & Straka, Jakub, 2022, Two new species of Xenos (Strepsiptera: Xenidae), parasites of social wasps of the genus Mischocyttarus (Hymenoptera: Vespidae) in the New World, Acta Entomologica Musei Nationalis Pragae 62 (1), pp. 185-195 : 186-190

Xenos bicolor Benda & Straka , sp. nov.

( Figs 1–2 , 5A )

Type locality. USA: Arizona, Cochise Country, Ash, Canyon Road 0.5 km W, Huachuca Mountains.

Type material. Hඈඅඈඍඒඉൾ: ♀ ( CNC), cephalothorax on mounting board (abdomen not preserved): “ USA: Aඋංඓඈඇൺ: Ash, Cyn. / Rd 0.5 km W, Cochise Co. / Huachuca Mts., 14.ii.1994 / N. McFerland lgt. // XFl9, host: / Mischocyttarus navajo / Bequaert, 1933”. Host: Mischocyttarus navajo Bequaert, 1933 . Pൺඋൺඍඒඉൾඌ: USA: Aඋංඓඈඇൺ: 1 ♀ ( CNC), with same data as for holotype; 3 EMP, same host, locality, and collector, 31.x.1993; 2 ♀♀, Ramsey Cyn., Siera Vista,Huachuca Mts., 26.viii.1967, R. Stenitzky lgt., host: Mischocyttarus navajo ; 1 ♀ ( KUNHM), Oak Criek Canyon, F. H. Snow lgt., host: Mischocyttarus navajo, J. Bequaert det.; 5 EMP ( CNC), Miller Cyn., Huachuca Mts., Cochise Co., 19.viii.1993, M. Sharkey lgt., host: Mischocyttarus navajo ; 1 EMP ( CNC), same locality, 25.v.1969, R. Stenitzky lgt., host: Mischocyttarus flavitarsis (Saussure, 1854) ; 1 ♀ + 4 EMP ( CNC), same host, locality, and collector, 5.xi.1969; 2 EMP ( KUNHM), Santa Rica Mts., 19.vii.1938, L. W. Hepner lgt., host: Mischocyttarus flavitarsis ; 1 ♀ + 1 EMP ( KUNHM), South Arizona, locality and date unknown, F. H. Snow lgt., host: Mischocyttarus flavitarsis . Nൾඐ Mൾඑංർඈ: 1 ♀ ( KUNHM), Ponderosa env., 13.vii.1991, B. Alexander lgt., host: Mischocyttarus navajo ; 2 ♀ ( KUNHM), Jemez Springs env., 01.vii.1941, R.H.Beamer lgt., host: Mischocyttarus flavitarsis . MEXICO: Nඎൾඏඈ Lൾඬඇ: 1 ♀ ( KUNHM), Linares env., 22.iii.1991,

R. Brooks & R. Leschen lgt., host: Mischocyttarus pallidipectus (Smith, 1857) ; 2 EMP ( KUNHM). HංൽൺඅGඈ: 5 MP ( KUNHM), Actopan env., 27.viii.1962, Ordway & Marston lgt., host: Mischocyttarus pallidipectus .

Diagnosis of female cephalothorax. Xenos bicolor sp. nov. differs from X. pallens sp. nov. and X. americanus ( Brèthes, 1923) by colouration of the cephalothorax. Anterior third of cephalothorax pale, posterior two thirds dark in contrast to X. pallens sp. nov. and X. americanus with cephalothorax almost completely pale ( Fig. 5 ). Differing from X. pallens sp. nov. by a larger size of cephalothorax: X. bicolor sp. nov. (length 0.90–1.14 mm, width 1.12–1.24 mm) versus X. pallens sp. nov. (length 0.80–0.86 mm, width 0.86–0.96 mm). Mesosternal and metasternal pigmented papillae not visible on dark background in X. bicolor sp. nov., but well visible in X. pallens sp. nov. Xenos bicolor sp. nov. differs from X. americanus by a smaller size of cephalothorax, X. americanus : length 1.43 mm, width 1.80 mm.

Xenos bicolor sp. nov. differs from superficially similar Xenos pecki Kirby, 1813 by following characters. Dark colouration of prosternum in X. pecki not reaching ventral border between head and cephalothorax; only prosternal extension pale brown in X. bicolor sp. nov. Maxilla elongated anteriorly in X. pecki ; in X. bicolor sp. nov. maxilla shorter, rather wider than long. For visual impression compare Figure 1C with Figure 51 in Bൾඇൽൺ et al. (2022). Description of female cephalothorax. Shape and colouration. Size of holotype cephalothorax: length 1.04 mm, width 1.22 mm. Cephalothorax variable but always wider than long, length 0.90–1.14 mm, width 1.12–1.24 mm. Meso-metathoracic segmental border very slightly constricted laterally, indistinct in some specimens. Anterior head margin slightly protruding, but distinctly in some individuals. Thorax distinctly widening posteriorly. Cephalothorax on ventral side with pale anterior part (head capsule and anterior part of prosternal extension) and dark posterior area (pst, Figs 1C , 5A ).

Head capsule. Length of head less than half of cephalothorax. Length proportion of head/cephalothorax 0.40 mm (0.40–0.45 mm) including lateral cephalic extension. Head colouration predominantly pale, not forming specific pattern. Only lower edge of mouth opening and area along border between head and prothorax distinctly darker. Clypeal region well delimited from labral area. Apical margin of clypeal area forming slightly protruding clypeal lobe (cll, Fig. 1C ), but distinctly protruding in some individuals (cll, Fig. 2A ). Numerous distinct sensilla present on clypeal surface, more or less evenly scattered. Cuticle of frontal region slightly wrinkled, reticulated (fr, Fig. 2B ). Segmental border between head and prothorax indicated by interrupted suture from dorsal side (sbhp, Fig. 2B ). Head and prothorax distinctly separated by birth opening ventromedially, and laterally by suture.

Supraantennal sensillary field slightly wrinkled with dispersed sensilla. Not delimited or indistinctly delimited by furrow medially, but border usually still recognisable (ssf, Fig. 2B ).

Antenna. Vestige of antennae present (details not investigated) (a, Fig. 2B ).

Labrum. Ventral field elliptic, not protruding. Dorsal field elongated, slightly arcuate, protuberant, ~ 4–5× (4× in holotype) wider than long in midline (dlf, Fig. 2A ). Dorsal field laterally as long as medially, with dispersed setae or sensilla inserted in small concavities.

Mandible anteromedially directed at angle of 40–50° (45° in holotype) and enclosed in mandibular capsule (md, Fig. 2A ). Mandibular bulge more or less distinctly raised, with several sensilla. Cuticle almost completely smooth. Tooth narrow, pointed apically.

Maxilla. Maxillae only partially fused with labial area, well demarcated from it, slightly raised but not distinctly projecting anteriorly from head capsule (mx, Fig. 2A ). Cuticle slightly wrinkled to reticulated, not distinctly sclerotized. Maxillary apex not projecting beyond mandible anteriorly, maxillary base not overlapping mandibular base, but at least in some individuals adjacent. Vestige of palp present, in some individuals very inconspicuous to almost invisible, located medially on ventral side of maxilla (mxp, Fig. 2A ). Maxillary base indistinctly produced anterolaterally as submaxillary groove, which is not part of maxilla; adjacent to border between head and prothorax.

Labium. Labial area recognisable between maxillae, delimited anteriorly by mouth opening and posteriorly by birth opening (lba, Fig. 2A ). Flat, as long as wide, in some individuals wider than longer. Cuticular surface very slightly reticulated.Anterior labial surface around mouth opening distinctly sclerotized and pigmented, posteriorly pale.

Mouth opening. Bisinuate in holotype. Very variable, widely arcuate, nearly straight or bisinuate, rarely nearly V-shaped, sclerotized along margin (os, Fig. 2A ).

Thorax. Pro-mesothoracic and meso-metathoracic borders well demarcated ventrally by mesal furrows (sbpm, sbmm, Fig. 1C ), indistinct dorsally. Border between metathorax and abdomen formed by ridge and indicated by change of cuticular sculpture. Thoracic segments constricted laterally between lateral cephalic extension and abdominal area around spiracles. Prosternal extension not indicated by specific cuticular sculpture or protuberance, evenly arched. Anterior part of prosternum pale, posterior part dark. Transition between colouration gradual, not sharp. Dark colouration reaches border between head and prosternum laterally. Cuticle of thoracic segments on ventral side with reticulate surface pattern. Prosternum with 7 to 37 (35 in holotype) conspicuous pigmented papillae in central pale area. Mesosternal and metasternal pigmented papillae not visible on a dark background. Colouration of meso- and metathorax dark ventrally and dorsally. Cuticle of dorsal side of thorax slightly reticulated, without papillae.

Abdominal segment I and spiracles. Lateral region of abdominal segment I below spiracles dark dorsally, similar as coloration of thorax. Spiracles located on posterior third of cephalothorax, slightly elevated, with anterodorsal (in holotype) or anterolateral orientation.

Diagnosis of male cephalotheca. Xenos bicolor sp. nov. differs from Xenos pallens sp. nov. by following characters. Cephalotheca with anterior protrusion, but apically blunt ( Fig. 2D ). Colouration predominantly dark with some slightly lighter areas forming specific pattern (cephalotheca of Xenos pallens sp. nov. paler). Gena between compound eye and mandible completely dark (gn, Fig. 2C ); conspicuously pale in Xenos pallens sp. nov. Occipital bulge absent. Maxilla completely dark (mx, Fig. 2C ).

Xenos bicolor sp. nov. differs from similar species Xenos pecki in several features. Cephalothorax shape of X. bicolor sp. nov. elliptic, occipital, and labial part not protruding; frontal impression (fi, Fig. 2C ) more distinct; diameter of genae between maxillary base and compound eye ~ 2.5× larger than diameter of vestigial antenna (~ 3× larger in X. pecki ). Compare Figure 2C with Figure 54 in Bൾඇൽൺ et al. (2022).

Description of male cephalotheca. Shape and colouration. In frontal view rounded and broadly elliptic, length 0.64–0.72 mm, width 0.84–0.92 mm; in lateral view slightly protruding anteriorly but with blunt apex. Colouration predominantly dark with some slightly lighter areas forming specific pattern.

Cephalothecal capsule. Entire compound eyes with light ground colour, well visible, with dark individual cornea lenses. Area around compound eye also slightly lighter than rest of cephalotheca. Genal region between compound eye and mandible completely dark (gn, Fig. 2C ). Clypeus paler than frons and labrum. Clypeal lobe distinctly arcuate in frontal view, prominent in lateral view but blunt anteriorly. Sensilla concentrated mainly on clypeal lobe. Frontal impression distinct (fi, Fig. 2C ). Occipital bulge absent (ob, Figs 2C, D ). Diameter of genal region between maxillary base and compound eye ~ 2.5× larger than diameter of vestigial antenna.

Supraantennal sensillary field. Dark, kidney-shaped and bulging, without furrows, delimited medially by distinct frontal impression.

Antenna of standard shape, dark, with small plates, and torulus usually complete, rarely incomplete ( Fig. 2C ). Periantennal area not clearly delimited from supraantennal sensillary field, dark.

Labrum. Labral area distinct, bulging. Dorsal field conspicuous, primarily dark with lighter central area, with dispersed setae well visible (dlf, Figs 2C, D ). Ventral field inconspicuous, completely dark (vlf, Fig. 2C ).

Mandible anteromedially to almost medially directed. Colouration lighter than that of maxilla, especially apically. Mandibular bulge with sensilla, separated from pointed tooth.

Maxilla distinct, prominent, completely dark (mx, Figs 2C, D ). Vestige of palp present.

Labium and hypopharynx. Labium distinctly visible between and below maxillae. Prementum and postmentum completely dark, separated by more or less distinct transverse furrow. Hypopharyngeal protuberance present but in some cases almost invisible (hyp, Figs 2C, D ).

Mouth opening well visible, not covered by ventral labral field, slightly or distinctly arcuate.

Hosts. Mischocyttarus navajo Bequaert, 1933 , Mischocyttarus flavitarsis (Saussure, 1854) , and Mischocyttarus pallidipectus (Smith, 1857) .

Phylogenetic relationships. Closely related species to X. pallens , part of a New World clade of Xenos containing a lineage parasitizing Polistes (Bൾඇൽൺ et al. 2021).

Etymology. From Latin, bicolor (= having two colours), referring to the colouration of the cephalothorax, with pale anterior region on both sides (head capsule and anterior part of prosternal extension) and dark posterior area; an adjective.

Distribution. USA: Arizona, New Mexico; Mexico: Hidalgo, Nuevo León.

Figures

Fig. 1. Xenos bicolor Benda & Straka sp. nov., host, female, cephalothorax. A – Mischocyttarus flavitarsis (Saussure, 1854) stylopised by X. bicolor sp. nov., lateral view; B – detail of host abdomen of M. navajo Bequaert, 1933, with two adult females; C–D – holotype of X. bicolor sp. nov. from M. navajo, cephalothorax; C – ventral side; D – dorsal side.Abbreviations: cll – clypeal lobe, lehc – lateral extension of head capsule, mst – mesosternum, mtst – metasternum, pst – prosternum (prosternal extension), sbmm – segmental border between mesothorax and metathorax, sbpm – segmental border between prothorax and mesothorax, sp – spiracle.

Fig. 2. Xenos bicolor Benda & Straka sp. nov., female, detail of cephalothorax, male, cephalotheca. A – detail of ventral side of cephalothorax from Mischocyttarus navajo Bequaert, 1933; B – detail of dorsal side of cephalothorax from M. flavitarsis (Saussure, 1854); C – frontal view of cephalotheca from M. pallidipectus (Smith, 1857); D – lateral view of cephalotheca from M. pallidipectus. Abbreviations: a – vestigial antenna, cl – clypeus, cll – clypeal lobe, coe – compound eye, dlf – dorsal labral field of labral area, fi – frontal impression, fr – frontal region, gn – gena, hyp – hypopharynx, lba – labial area, md – mandible, mx – vestige of maxilla, mxb – maxillary base, mxp – vestige of maxillary palp, ob – occipital bulge, os – mouth opening, pom – postmentum, prm – prementum, pst – prosternum (prosternal extension), sbhp – segmental border between head and prothorax, smxg – submaxillary groove, ssf – sensillum of supraantennal sensillary field, vlf – ventral labral field of labral area.

Fig. 5. Schematic drawing of cephalothorax of all known Xenos species parasitizing wasps of the genus Mischocyttarus Saussure, 1853. A – X. bicolor Benda & Straka sp. nov.; B – X. pallens Benda & Straka sp. nov., C – X. americanus (Brèthes, 1923).