Tuberoxenos, Benda & Pohl & Nakase & Beutel & Straka, 2022

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

Tuberoxenos gen. nov.

Type species.

Xenos sphecidarum Siebold, 1839, here designated.

Diagnosis of female cephalothorax.

Distinguished from Pseudoxenos by conspicuously convex, round cephalothorax (Fig. 43C ), and distinctly raised, anteriorly protruding dorsal labral field (Fig. 45D ). Differring from other genera by the following combination of characters. Maxilla well-developed and clearly separated from labial area, prominent and directed anteriorly (Fig. 45E ). Mandibular tooth narrow or slightly widened. Prosternal extension undifferentiated, evenly arched but in some cases protruding and overlapping with maxillolabial area and posterior part of mandibles. Differing from Nipponoxenos by mandible nested in capsule. In contrast to Paragioxenos , head and prothorax ventrally delimited by birth opening medially and by suture laterally.

Description of female cephalothorax.

Shape and coloration. Compact, ca. as long as wide or longer than wide. In ventral view appearing conspicuously convex, rotund (Fig. 43C ), high-elliptic in cross-section. Species rather constant in size, length 1.06-1.34 mm, maximum width 0.94-1.4 mm. Anterior head margin evenly rounded or very slightly protruding. Thorax slightly or distinctly widening posteriorly. Coloration with multiple brown shades forming distinct pattern, mostly dark.

Head capsule. Ca. ⅓ - ⅖ as long as entire cephalothorax including lateral cephalic extension. Coloration of head dominantly pale or brown, forming specific color pattern. Clypeal region well delimited from labral area, arcuate, or very slightly protruding and forming clypeal lobe. Surface smooth or slightly wrinkled. Ca. 50-95 sensilla regularly dispersed on clypeal area. Border between clypeal area and frontal region clearly recognizable or indistinct. Frontal region smooth or slightly wrinkled. Segmental border between head and prothorax quite distinct on dorsal side, indicated by furrow, change in cuticular sculpture or coloration.

Supra-antennal sensillary field. Slightly wrinkled or reticulated, delimited by more or less distinct furrow on medial side (Fig. 45B ).

Antenna. Preserved as poorly defined area, in some cases indistinct (Fig. 44C ). With cavities, several small, rounded plates, or sensilla, the latter combined in some cases. Periantennal area smooth or slightly wrinkled (Fig. 44C ).

Labrum. Ventral field at least slightly wider than long, elliptical or semicircular. Dorsal field widely arcuate, ~ 5 × wider than long in midline, distinctly raised (Fig. 45D ). Dorsal field with ~ 17-28 pointed or blunt setae on its surface.

Mandible. Anteromedially directed at angle of 20-40°, enclosed in mandibular capsule. Mandibular bulge slightly or distinctly raised, with several sensilla. Cuticle smooth, slightly sculptured or reticulated. Longitudinal grooves on articular area present. Tooth narrow, pointed, more or less armed with spines.

Maxilla. Well developed and clearly separated from labial area, prominent and anteriorly directed. Protruding maxillary part usually slightly overlapping with proximal portion of mandible (Fig. 45E ), but not projecting beyond mandible anteriorly. Cuticle smooth or very slightly wrinkled. Vestige of palp inconspicuous, preserved as small bulge with indistinct plates, located anteromedially on ventral side of maxilla (Fig. 45E ). Maxillary base distinctly produced anterolaterally as submaxillary groove.

Labium. Labial area distinct between maxillae, delimited anteriorly by mouth opening and posteriorly by birth opening. Labial area wider than long in midline, flat or slightly convex. Cuticular surface smooth or slightly reticulated.

Mouth opening. Arcuate, nearly straight, or bi-arcuate, sclerotized marginally.

Thorax and abdominal segment I. Pro-mesothoracic and meso-metathoracic borders distinct, usually separated by mesal furrows, often combined with color stripes or spots on dorsal and ventral sides. Border between metathorax and abdomen usually indicated by change of cuticular sculpture and very indistinct ridge. Cuticle of thoracic segments on ventral side reticulate with scattered small and pigmented papillae. Dorsal side of thorax smooth or slightly reticulated. Prosternal extension undifferentiated, prosternal margin evenly arched but in some cases protruding and overlapping with maxillolabial area and posterior part of mandibles. Meso- and metathorax of standard transverse shape. Setae present on lateral region of abdominal segment I (Fig. 44 E, F ).

Spiracles. Spiracles on posterior half or third of cephalothorax slightly elevated, with lateral or anterolateral orientation.

Diagnosis of male cephalotheca.

Differing from other genera by the following combination of characters. Diameter of genae between maxillary base and compound eye ~ 1.5 × larger than diameter of vestigial antenna. Occipital bulge absent and frontal impression indistinct or missing. Distinct paired furrows of supra-antennal sensillary field present (Fig. 46A, D ). Cephalotheca always appearing rotund.

Description of male cephalotheca.

Shape and coloration. In frontal view rounded, almost circular (Fig. 46A ), in lateral view pointed anteriorly. Coloration forming pattern of pale and dark shades.

Cephalothecal capsule. Compound eyes with darker individual ommatidia well visible on pale ocular background. Conspicuous clypeal lobe arcuate in frontal view, prominent in lateral view. Sensilla dispersed over entire clypeal area. Paired furrows of supra-antennal sensillary field distinctly presented but impression lacking on frontal region. Occipital bulge absent. Diameter of genae between maxillary base and compound eye small, ~ 1.5 × larger than diameter of vestigial antenna.

Supra-antennal sensillary field. Kidney-shaped and bulging, medially delimited by distinct furrow (Fig. 46A, D ).

Antenna. Large, with complete torulus. Periantennal area not clearly delimited from supra-antennal sensillary field. Small plates, cavities and sensilla present (Fig. 46C ).

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

Mandible. Anteromedially directed. Tooth pointed, not reaching area of mandibular bulge basally. Bulge with sensilla.

Maxilla. Distinct, prominent. Coloration completely dark or brighter around distinct vestige of maxillary palp.

Labium and hypopharynx. Labium distinct between and below maxillae, dark. Praementum and postmentum separated by furrow. Hypopharyngeal protuberance indistinct or absent.

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

Phylogenetic relationships.

Deeply nested within Xenidae ( Benda et al. 2019, 2021), part of a clade of an Old Word origin, with Pseudoxenos Saunders as sister group.

Diversity and distribution.

A lineage of Afrotropical-Palearctic origin, comprising 5 currently valid species, restricted to these regions. It is an example of connectivity between both biogeographic regions ( Benda et al. 2019).

Hosts.

Ammophila and Podalonia spp. ( Sphecidae : Ammophilinae ), rarely Prionyx spp. ( Sphecidae : Sphecinae ).

Etymology.

From the Latin substantive tuber, meaning a swelling. The name refers to conspicuous swellings on the host abdomen caused by protruded xenid specimens under tergites or sternites. Gender masculine.

Comments.

All described species of Tuberoxenos gen. nov. were previously placed in Paraxenos based on parasitising Sphecidae ( Kinzelbach 1971b). Despite this concept, this group is morphologically well defined. We classify it as a separate genus, based on molecular phylogenies ( Benda et al. 2019, 2021) and morphological characters newly reported in this paper.

Figures

Figure 43. Tuberoxenos sphecidarum, host, male, female, cephalothorax, photomicrographs A Podalonia tydei stylopized by females of T. sphecidarum, lateral view B detail of host abdomen with three adult females inside C ventral side of female cephalothorax D dorsal side of female cephalothorax.

Figure 44. Tuberoxenos sphecidarum, female, cephalothorax, SEM micrographs A ventral side B dorsal side C left vestigial antenna, dorsal side D right vestigial antenna, dorsal side E left lateral border of abdominal segment I below spiracle, dorsal side F right lateral border of abdominal segment I below spiracle, dorsal side. Abbreviations: a - vestigial antenna, paa - periantennal area.

Figure 45. Tuberoxenos sphecidarum, female, cephalothorax, SEM micrographs A anterior part of cephalothorax, ventral side B anterior part of cephalothorax, dorsal side C mouthparts, ventral side D detail of anterior border of cephalothorax, ventral side E right mandible and maxilla, ventral side F left mandible and maxilla, ventral side. Abbreviations: dlf - dorsal field of labral area, fr - frontal region, fssf - furrow of supra-antennal sensillary field, mx - vestige of maxilla, mxp - vestige of maxillary palp, smxg - submaxillary groove, ssf - supra-antennal sensillary field.

Figure 46. Tuberoxenos sphecidarum, male, cephalotheca, photomicrographs, SEM micrographs A frontal view B lateral view C vestigial antenna D frontal view E mouthparts. Abbreviations: fssf - furrow of supra-antennal sensillary field, mx - vestige of maxilla.