Xenos pallens 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 : 190-191

Xenos pallens Benda & Straka , sp. nov.

( Figs 3–4 , 5B )

Type locality. Costa Rica: Puntarenas, San Vito env., Las Alturas.

Type material. Hඈඅඈඍඒඉൾ: ♀ ( CNC), cephalothorax on mounting board (abdomen not preserved). “ COSTA RICA: / Pඎඇඍൺඋൾඇൺඌ: San Vito / env., Las Alturas, 1500 m / 16.viii.1995 / J. R. Vockeroth lgt. // Brsp2 / host: Mischocyttarus / costaricensis Richards , / 1945” Host: Mischocyttarus costaricensis Richards, 1945 . Pൺඋൺඍඒඉൾඌ: 2 ♀♀ + 1 MP ( CNC), from the same host specimen as holotype.

Diagnosis of female cephalothorax. Differing from X. bicolor sp. nov. and X. americanus by following characters. Cephalothorax almost completely pale as in X. americanus , but in contrast to X. bicolor sp. nov. with posterior two thirds dark. Some parts of cephalothorax, especially maxillae and abdominal areas, dark and sclerotized. Smallest known species parasitizing Mischocyttarus wasps: cephalothorax length: 0.80–0.86 mm, width 0.86–0.96 mm. Other two species significantly larger: X. bicolor sp. nov. (length 0.90–1.14 mm, width 1.12–1.24 mm), X. americanus (length 1.43 mm, width 1.80 mm). Mesosternal and metasternal pigmented papillae well visible, in contrast to X. bicolor sp. nov. where papillae are unrecognizable on dark posterior part of cephalothorax.

Description of female cephalothorax. Shape and colouration. Size of cephalothorax of holotype: length 0.80 mm, width 0.86 mm. Shape of cephalothorax somewhat variable but always slightly wider than long, length 0.80–0.86 mm, width 0.86–0.96 mm. Meso-metathoracic segmental border region usually very slightly constricted laterally, but not in all individuals. Anterior head margin protruding in holotype, usually but not always slightly protruding. Thorax slightly widening posteriorly. Colouration mostly pale, with shades of light brown dominating. Some parts of cephalothorax, especially maxillae and abdominal regions, dark and sclerotized.

Head capsule. Length of head slightly less than half of cephalothorax, proportion head/cephalothorax 0.45 (0.44–0.47) including lateral cephalic extension. Head colouration predominantly pale, not forming specific pattern. Only maxillae, lower edge of mouth opening, and area along border between head and prothorax distinctly darkened. Clypeal region well delimited from labral area. Clypeal lobe on apical margin of clypeal area usually but not always protruding (compare cl on Figs 3C , 4A ). Numerous sensilla present on clypeal surface, scattered through clypeal surface but mainly concentrated medially. Cuticle of frontal region slightly wrinkled, reticulated (fr, Fig. 4B ). Segmental border between head and prothorax indicated by indistinct coloured stripes laterally and by transition of colouration on dorsomedian region (sbhp, Fig. 4B ). On ventral side head and prothorax distinctly separated by birth opening medially, and by a suture laterally.

Supraantennal sensillary field slightly wrinkled, with dispersed sensilla (ssf, Fig. 4B ). Medial paired furrows indistinct.

Antenna. Vestige not investigated.

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

Mandible anteromedially directed at angle of 45° (40–50°), enclosed in mandibular capsule (md, Fig. 4A ). Mandibular bulge more or less distinctly raised, with several sensilla. Cuticle of mandible partially smooth and partially wrinkled. Tooth narrow, wider in some individuals, directing ventrally or apically.

Maxilla partially fused with labial area but distinguishable from it, slightly raised anterolaterally near mandible but not distinctly prominent (mx, Fig. 4A ). Cuticle slightly wrinkled to reticulated, distinctly sclerotized. Maxillary apex not projecting beyond mandible anteriorly, maxillary base not overlapping with mandibular base but adjacent. Vestige of palp presented, very inconspicuous, located medially on ventral side of maxilla. Maxillary base distinctly produced anterolaterally as submaxillary groove, well visible as dark interrupted line parallel to border between head and prothorax (mdb, smxg, Fig. 4A ).

Labium. Labial area recognisable between maxillae, delimited anteriorly by mouth opening and posteriorly by birth opening. Flat, wider than long, cuticular surface very slightly reticulated. Anterior labial surface around mouth opening distinctly sclerotized and darkened; posterior region pale (lba, Fig. 4A ).

Mouth opening widely arcuate in holotype. Variable, slightly arcuate in some individuals, medially nearly straight, distinctly sclerotized at margin (os, Fig. 4A ).

Thorax. Pro-mesothoracic and meso-metathoracic borders distinct ventrally, indicated by mesal furrows (sbpm, sbmm, Fig. 4A ), borders on dorsal side indistinct. Border between metathorax and abdomen usually formed by ridge or indicated by change of cuticular sculpture. Thoracic segments constricted laterally between lateral cephalic extension and abdominal area around spiracles. Prosternal extension without different cuticular sculpture or protuberance, evenly arched. Whole prosternum pale. Cuticle of thoracic segments on ventral side reticulate to nearly smooth. Prosternum in the centre with conspicuous pigmented papillae. In three available cephalothoraces 29 (holotype), 32, or 51 prosternal papillae (pstp, Fig. 4A ). Mesosternal papillae forming two groups each situated close to lateral margin, each group containing 7 (7 – 17) papillae. Metasternal group contains 5 (5 – 18) papillae. In contrast to prosternum, pigmented papillae absent medially on mesosternum and metasternum (mstp, mtstp, Fig. 4A ). Colouration of meso- and metathorax pale on both sides. Cuticle of dorsal side of thorax slightly reticulated, without papillae.

Abdominal segment I and spiracles. Lateral region of abdominal segment I below spiracles darker on dorsal side, contrasting to pale thorax. Spiracles on posterior half of cephalothorax very slightly elevated, with anterolateral (holotype) or anterodorsal orientation.

Diagnosis of male cephalotheca. Xenos pallens sp. nov. differs from X. bicolor sp. nov. by a combination of characters. Cephalotheca protruding anteriorly, pointed apically ( Fig. 4C ). Colouration predominantly dark, but overall lighter than in X. bicolor sp. nov., with extensive bright areas forming specific pattern. Part of genal region bordering mandible, maxilla, and labium conspicuously pale (gn, Fig. 4C ). Occipital bulge very indistinct but present (ob, Figs 4C, D ); absent in X. bicolor sp. nov. Maxillary base pale, anterior part of maxilla and vestige of palp entirely dark (mx, Fig. 4C ); maxilla completely dark in X. bicolor sp. nov.

Description of male cephalotheca. Shape and colouration. In frontal view rounded and broadly elliptic, length 0.74 mm, width 0.90 mm; in lateral view protruding anteriorly, pointed apically. Colouration predominantly dark with some extensive pale areas forming specific pattern.

Cephalothecal capsule. Entire compound eyes pale, well visible, with darker remnants of individual cornea lenses visible. Genal region around eyes pale laterally but darker medially. Areas of gena bordering with mandible, maxilla, and labium conspicuously pale (gn, Fig. 4C ). Clypeus moderately pale. Clypeal lobe distinctly arcuate in frontal view, prominent in lateral view, pointed. Sensilla mainly concentrated on clypeal lobe. Frontal impression distinct (fi, Fig. 4C ). Occipital bulge very indistinct (ob, Figs 4C, D ). Diameter of gena between maxillary base and compound eye ~ 2.5 larger than diameter of vestigial antenna.

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

Antenna of standard shape, dark, with small plates and complete torulus ( Fig. 4C ). Periantennal area not clearly delimited from supraantennal sensillary field, dark coloured.

Labrum. Labral area distinct. Dorsal field conspicuous, mostly dark but lighter on central area, with dispersed setae well visible. Ventral field inconspicuous, entirely dark.

Mandible orientation almost straight towards midline. Colouration overall lighter than posterior part of maxilla. Mandibular bulge with sensilla, separated from pointed tooth.

Maxilla distinct, prominent. Vestige of palp present. Maxillary base bright, anterior part and vestige of palp entirely dark (mx, Fig. 4C ).

Labium and hypopharynx. Labium distinctly visible between and below maxillae. Prementum and postmentum entirely dark, separated by more or less distinct transverse furrow. Hypopharyngeal protuberance absent.

Mouth opening. Well visible, not covered by ventral labral field, slightly arcuate.

Host. Mischocyttarus costaricensis Richards, 1945 .

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

Etymology. From Latin pallens (= pale, yellowish), referring to the characteristic pale colouration of the female cephalothorax; an adjective.

Distribution. Costa Rica.

Figures

Fig. 3. Xenos pallens Benda & Straka sp. nov., host, female, cephalothorax. A – Mischocyttarus costaricensis Richards, 1945, stylopised by X. pallens sp. nov., lateral view; B – the same specimen, dorsal view; C – holotype of X. pallens sp. nov., ventral side of cephalothorax; D – holotype of X. pallens sp. nov., dorsal side of cephalothorax. Abbreviation: cl – clypeus.

Fig. 4. Xenos pallens Benda & Straka sp. nov., female, cephalothorax, male, cephalotheca. A – ventral side of cephalothorax; B – dorsal side of cephalothorax; C – frontal view of cephalotheca; D – lateral view of cephalotheca. Abbreviations: a – vestigial antenna, cl – clypeus, 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, mst – mesosternum, mstp – mesosternal papilla, mtst – metasternum, mtstp – metasternal papilla, mx – vestige of maxilla, mxb – maxillary base (at mandible base), mxp – vestige of maxillary palp, ob – occipital bulge, os – mouth opening, pom – postmentum, prm – prementum, pst – prosternum (prosternal extension), pstp – prosternal papilla, sbhp – segmental border between head and prothorax, sbmm – segmental border between mesothorax and metathorax, sbpm – segmental border between prothorax and mesothorax, smxg – submaxillary groove, sp – spiracle, 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).