Nipponoxenos Kifune & Maeta, 1975, stat. res.

Benda, Daniel, Pohl, Hans, Nakase, Yuta, Beutel, Rolf & Straka, Jakub, 2022, A generic classification of Xenidae (Strepsiptera) based on the morphology of the female cephalothorax and male cephalotheca with a preliminary checklist of species, ZooKeys 1093, pp. 1-134 : 1

Nipponoxenos Kifune & Maeta, 1975, stat. res.

Nipponoxenos Kifune & Maeta, 1975: 446 (as a subgenus of Xenos Rossi). Type species: Xenos (Nipponoxenos) vespularum Kifune & Maeta, 1975, by original designation.

Diagnosis of female cephalothorax.

Differing from most genera in following combination of characters. Mandibles protruding distinctly from mandibular capsule, reaching or slightly projecting beyond cephalic edge (Fig. 10A ). Maxilla anteriorly directed, strongly sclerotized. Maxillary bases conspicuously wide, connected in midline along birth opening. Anterior part of maxilla pointed (Fig. 10A ). In contrast to Paragioxenos , head and prothorax ventrally delimited by birth opening medially and by suture laterally. Cephalothorax mostly pale.

Description of female cephalothorax.

Shape and coloration. Cephalothorax distinctly longer than wide, length 2.0 mm, maximum width 1.76 mm. Anterior head margin not protruding. Thorax nearly straight. Meso-metathoracic border slightly constricted (Fig. 9C ). Coloration with distinct pattern of different pale brown shades; usually medially pale and slighter darker laterally in ventral and dorsal view.

Head capsule. Almost ⅓ as long as entire cephalothorax including lateral cephalic extensions. Coloration mostly pale brown, but darker on lateral extensions and on distinctly sclerotized maxillae (Fig. 10A ). Clypeal area delimited from labral area, slightly protruding anteriorly, forming inconspicuous, slightly pigmented clypeal lobe (Fig. 10A ); clypeal sensilla present. Border between clypeal and frontal region distinct. Cuticle of frontal region slightly wrinkled. Segmental border between head and prothorax indistinct dorsally but indicated by coloration; on ventral side separated by birth opening medially and by suture laterally.

Supra-antennal sensillary field. Not delimited by furrow mesally.

Antenna. Presence or absence of antennal vestige not verified.

Labrum. Ventral labral field elliptic, not protruding but slightly convex. Dorsal labral field elliptic, ~ 5 × wider than long, slightly arcuate. Presence or absence of labral sensilla not verified.

Mandible. Anteromedially directed at angle of 60°, distinctly protruding from mandibular capsule, reaching or slightly projecting beyond anterior edge of head (Fig. 10A ). Bulge not distinctly raised. Sensilla not examined. Mandibular tooth narrow or moderately widened, pointed apically.

Maxilla. Anteriorly directed, pointed, strongly sclerotized. Bases wide, connected medially. Apical region not projecting beyond mandible anteriorly. Presence of palp vestige not verified. Submaxillary groove slightly produced.

Labium. Labial area inserted between maxillae, slightly pigmented medially; anteriorly delimited by mouth opening and posteriorly by connected maxillary bases.

Mouth opening. Mouth opening slightly curved, sclerotized along margin.

Thorax and abdominal segment I. Pro-mesothoracic and meso-metathoracic borders vaguely indicated ventrally by pigmented stripes with specific cuticular surface, but nor recognizable on dorsal side (Fig. 9C, D ). Border between metathorax and abdomen marked by ridge and change of cuticular sculpture and pigmentation. Entire abdominal segment I darker than thorax. Cuticle of thoracic segments on ventral side wrinkled or reticulate, with several small, pigmented papillae on prothorax. Prosternal extension undifferentiated, evenly arched. Dorsal side of thorax mostly smooth. Meso- and metathorax unmodified in shape, transverse. Setae and cuticular spines on lateral region of abdominal segment I not examined.

Spiracles. Situated on posterior ⅓ of cephalothorax, slightly elevated, with anterolateral orientation.

Diagnosis of male cephalotheca.

Less pigmented than in other genera of Xenidae . With conspicuous, nearly black clypeus and very short and black genae, very distinct on lightly colored surrounding areas of cephalotheca (Fig. 11 ). Antennal vestige very large (Fig. 11A ).

Description of male cephalotheca.

Shape and coloration. Rounded laterally in frontal view, widely elliptic (Fig. 11A ); rounded in lateral view (Fig. 11B ). Coloration pale except for clypeus and genae (Fig. 11 ).

Cephalothecal capsule. Compound eyes with individual ommatidia well visible. Clypeus black colored; inconspicuous clypeal lobe straight in frontal view; sensilla mainly concentrated on clypeal lobe and on lateral parts of clypeus. Frontal region not deformed, lacking frontal impression. Occipital bulge rather indistinct. Diameter of genae (black) between maxillary base and compound eye very small, subequal to antennal diameter (Fig. 11A ). Occipital bulge absent.

Supra-antennal sensillary field. Kidney-shaped and bulging, delimited medially by quite indistinct furrow.

Antenna. Antennal vestige very large, with complete torulus. Periantennal area distinctly delimited.

Labrum. Labral area distinct. Setae of dorsal field present.

Mandible. Anteromedially directed. Coloration darker anteriorly and less pigmented posteriorly. Bulge pointed.

Maxilla. Distinct, prominent. Coloration darker anteriorly, posterior part around vestige of palp less pigmented.

Labium and hypopharynx. Located between and below maxillae. Praementum and postmentum distinct, separated by slightly paler coloration of postmentum. Hypopharyngeal protuberance inconspicuous.

Mouth opening. Mouth opening distinctly arcuate, nearly U-shaped.

Phylogenetic relationships.

One of the earliest diverging lineages of Xenidae with a Palearctic origin ( Benda et al. 2019). Placed either as sister to Tachytixenos Pierce + Paraxenos Saunders or as the earliest diverging group, sister to all other Xenidae ( Benda et al. 2021).

Diversity and distribution.

Monotypic, restricted to East Asia.

Hosts.

Vespula spp. ( Vespidae : Vespinae ).

Comments.

The monotypic Nipponoxenos was originally described as a subgenus of Xenos by Kifune and Maeta (1975). We classify it as a valid genus, based on a molecular phylogeny ( Benda et al. 2019) and morphological characters newly reported here.

Figures

Figure 9. Nipponoxenos vespularum Kifune & Maeta, host, male, female, cephalothorax, photomicrographs A Vespula shidai Ishikawa, Sk. Yamanne & Wagner stylopized by male of N. vespularum, lateral view B detail of host abdomen with male puparium inside C ventral side of female cephalothorax D dorsal side of female cephalothorax. Abbreviation: sbmm - segmental border between mesothorax and metathorax.

Figure 10. Nipponoxenos vespularum Kifune & Maeta, anterior part of female cephalothorax, photomicrographs A anterior part of cephalothorax, ventral side B Anterior part of cephalothorax, dorsal side. Abbreviations: cll - clypeal lobe, md - mandible, mx - vestige of maxilla (maxilla), pp - pigmented papillae.

Figure 11. Nipponoxenos vespularum Kifune & Maeta, male, cephalotheca, photomicrographs A frontal view B lateral view. Abbreviations: a - vestigial antenna, cl - clypeus, coe - compound eye, gn - gena, mxb - maxillary base.