Pseudoxenos Saunders, 1872

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

publication ID	https://dx.doi.org/10.3897/zookeys.1093.72339
publication LSID	lsid:zoobank.org:pub:23B70708-49A9-4681-AC20-494D06F98CCE
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scientific name	Pseudoxenos Saunders, 1872
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Pseudoxenos Saunders, 1872 View in CoL

Pseudoxenos Saunders, 1872: 44. Type species: Pseudoxenos schaumii Saunders, 1872, by original designation.

Diagnosis of female cephalothorax.

Differs from Tuberoxenos by flat dorsal field of labrum (Fig. 41C View Figure 41 ) and more flattened cephalothorax, with more or less even shape (Fig. 39C View Figure 39 ), appearing flattened-elliptical in cross section. Distinguished from Deltoxenos by dorsal labral field laterally as long as along midline (Fig. 41C, D View Figure 41 ), and meso-metathoracic segmental border not constricted laterally. In contrast to Macroxenos lateral parts of abdomen posterior to spiracles with dark coloration (Fig. 39D View Figure 39 ). Mandible nested in mandibular capsule. In contrast to Paragioxenos , head and prothorax ventrally delimited by the birth opening in middle region and laterally by a suture.

Description of female cephalothorax.

Shape and coloration. Compact, longer than wide, elliptic in cross-section. Meso-metathoracic segmental border not constricted laterally. Size fairly constant, length 1.08-1.44 mm, maximum width 1.02-1.4 mm. Anterior head margin rounded or protruding. Thorax slightly widening posteriorly. Coloration with multiple brown shades forming pattern.

Head capsule. Ca. ⅖ as long as entire cephalothorax including lateral extensions. Coloration mostly dark brown, often with specific patterns. Clypeal region delimited from labral area (Fig. 41D View Figure 41 ), arcuate, or protruding and forming clypeal lobe. Surface smooth or slightly wrinkled. Approximately 35-56 sensilla mainly concentrated anteriorly but dispersed over entire clypeal area. Border between clypeal area and frontal region hardly distinct but still recognizable. Frontal surface smooth (Fig. 40F View Figure 40 ). Segmental border between head and prothorax clearly recognizable or indistinct on dorsal side, often indicated by dark brown stripes, and in some cases with two distinct dark spots on mesal region (Fig. 39D View Figure 39 ).

Supra-antennal sensillary field. Smooth or slightly wrinkled, with dispersed sensilla. Furrow forming border on medial side more or less distinct (Fig. 41B View Figure 41 ).

Antenna. Preserved as poorly defined area, sometimes raised, usually with several small, rounded plates, rarely with additional sensilla or cavity (Fig. 40C View Figure 40 ). Periantennal area smooth.

Labrum. Ventral field distinctly wider than long, elliptic. Dorsal field nearly straight, slightly arcuate, at least 4-5 × wider than long in midline, flat and smooth, with 15-21 clearly visible setae inserted in cavities (Fig. 41C, D View Figure 41 ). Dorsal field laterally as long as medially, in some cases almost merging with head capsule.

Mandible. Mandibles anteromedially directed at an angle of 35-45° and nested in mandibular capsule. Mandibular bulge not or slightly raised, bears several sensilla. Cuticle of mandible sculptured to nearly smooth. Mandibular tooth narrow, pointed, straight or hook-shaped, armed with spines.

Maxilla. Separated from labial area, slightly or distinctly protruding, prominent portion directed anteriorly or anterolaterally, maxilla slightly overlapping with mandible proximally (Fig. 41F View Figure 41 ), but not projecting beyond it anteriorly. Cuticle usually smooth, rarely wrinkled. Vestige of palp very distinct, with more or less distinct plates or cavity, located medially on ventral side of maxilla. Submaxillary groove more or less distinctly produced posterolaterally to maxillary base.

Labium. Labial area between maxillae flat but distinct, relatively large, delimited anteriorly by mouth opening and posteriorly by birth opening. As long as wide or longer than wide. Cuticular surface in most cases largely smooth and shiny, or faintly and uniformly sculptured.

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

Thorax and abdominal segment I. Pro-mesothoracic and meso-metathoracic borders more or less distinct, separated by mesal furrows. Border between metathorax and abdomen formed by ridge. Cuticle of thoracic segments on ventral side reticulate with scattered small and pigmented papillae. Cuticle of dorsal side of thorax smooth or slightly wrinkled. Prosternal extension undifferentiated, anterior margin evenly arched. Meso- and metathorax transverse. Lateral parts of abdomen posterior to spiracle dark (Fig. 39D View Figure 39 ). Setae present on lateral region of abdominal segment I.

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

Diagnosis of male cephalotheca.

Diameter of genae between maxillary base and compound eye ~ 1.5 × as large as diameter of vestigial antenna. Occipital bulge present (Fig. 42D View Figure 42 ). Frontal region very distinctly deformed by frontal impression (Fig. 42D View Figure 42 ). Distinct paired furrows of supra-antennal sensillary field absent.

Description of male cephalotheca.

Shape and coloration. In frontal view rounded laterally, flattened, elliptical, in lateral view pointed anteriorly. Coloration with pattern of pale and dark shades.

Cephalothecal capsule. Compound eyes with darker individual ommatidia well visible on pale ocular background. Clypeal lobe straight or slightly arcuate in frontal view, prominent in lateral view. Sensilla mainly concentrated medially. Frontal impression distinctly present (Fig. 42D View Figure 42 ). Occipital bulge present (Fig. 42D View Figure 42 ). Diameter of genae between maxillary base and compound eye small, ~ 1.5 × diameter of vestigial antenna.

Supra-antennal sensillary field. Kidney-shaped and bulging, delimited medially by frontal impression, without distinct furrows.

Antenna. Vestiges large, with complete torulus. Periantennal area not clearly delimited from supra-antennal sensillary field. Small plates or sensilla present (Fig. 27C View Figure 27 ).

Labrum. Labral area distinct, with setae on dorsal field.

Mandible. Anteromedially directed. Mandibular bulge with sensilla, separated from pointed tooth.

Maxilla. Distinct, prominent. Coloration completely dark. Vestige of palp distinct.

Labium and hypopharynx. Labium distinct between and below maxillae, dark. Praementum and postmentum distinctly separated by furrow. Hypopharyngeal protuberance present.

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 Tuberoxenos gen. nov. as sister group.

Diversity and distribution.

A group of Palearctic origin ( Benda et al. 2019), comprising seven currently valid species restricted to this region.

Hosts.

Various genera of Odynerini ( Vespidae : Eumeninae ).

Comments.

Pseudoxenos was described by Saunders (1872) but only a superficial description of the male was provided. Bohart (1937) synonymized many names previously designed ( Eupathocera , Ophthalmochlus , Homilops , Leionotoxenos Sceliphronecthrus, Macroxenos ) with Pseudoxenos . Although later Kinzelbach (1971b) used Pseudoxenos for all xenids parasitising solitary Vespidae worldwide, the genus corresponds to a Palearctic clade utilizing Odynerini according to the molecular phylogeny of Benda et al. (2019, 2021). We classify this lineage as a separate genus, based on these molecular phylogenic works and morphological characters newly reported here.