Leionotoxenos Pierce, 1909, 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

Leionotoxenos Pierce, 1909, stat. res.

Leionotoxenos Pierce, 1909: 137. Type species: Leionotoxenos jonesi Pierce, 1909, by original designation.

Pseudoxenos Saunders, 1872 (partim!) (synonymy proposed by Bohart, 1937: 133). Paraxenos Saunders, 1872 (partim!) (synonymy proposed by Kinzelbach 1971b: 162).

Monobiaphila Pierce, 1909: 139 (syn. nov.). Type species: Monobiaphila bishoppi Pierce, 1909, by original designation.

Montezumiaphila Brèthes, 1923: 45 (syn. nov.). Type species: Montezumiaphila vigili Brèthes 1923, by monotypy.

Diagnosis of female cephalothorax.

Differing from its sister genus Eupathocera in the following characters. Frontal region with conspicuous coverage of papillae (Fig. 25F ). Supra-antennal sensillary field with wrinkled surface, which almost reaches vestigial antenna. Periantennal area small and indistinct (Fig. 25C ). Prothorax ventrally connected to head on same plane, versus usually elevated in Eupathocera (Fig. 25A ). Position of sensilla on clypeal lobe not extended onto ventral side of clypeal area as in Xenos or Paraxenos . Rudiments of torulus usually preserved (Figs 25C , 29D ). Mandible not protruding from mandibular 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. Cephalothorax compact and usually ovoid, varying distinctly in shape, longer than wide to distinctly wider than long. Species relatively variable in size, length 0.88-1.7 mm, maximum width 0.72-1.68. Anterior head margin evenly rounded or slightly protruding anteriorly. Thorax slightly to strongly widening posteriorly, sometimes subparallel. Coloration of cephalothorax with multiple dark and light brown shades forming distinct pattern (Fig. 24C, D ).

Head capsule. Ca. ⅓ to nearly ½ as long as entire cephalothorax including lateral cephalic extensions. Coloration variable, pale to dark brown or forming specific patterns. Clypeal area well delimited from labral region, clypeal lobe indistinct or slightly protruding anteriorly. Surface more or less wrinkled, in some cases with reticulated pattern (Fig. 26D ), with 12-26 (or more) sensilla distributed anteriorly. Border between clypeal and frontal region indistinct but still recognizable. Frontal region with conspicuous coverage of papillae (Fig. 25F ). Dorsal border between head and prothorax indicated by interrupted suture, distinct coloration, or largely obliterated.

Supra-antennal sensillary field. Conspicuously wrinkled or reticulated. Usually delimited by indistinct furrow on medial side, but otherwise by change in cuticular sculpture, with wrinkled surface of supra-antennal sensillary field versus papillae on frontal region (Fig. 26B ).

Antenna. Preserved as more or less defined area, with several rounded plates and setae (Fig. 25C ). Torulus largely reduced or absent, rudiment usually recognizable as interrupted furrow (Fig. 25C ). Periantennal area small and indistinct, supra-antennal sensillary field with wrinkled surface almost reaching antennal vestige (Fig. 25C ).

Labrum. Ventral field wider than long, elliptic. Dorsal field slightly arcuate, at least 3 × to 4 × wider than medially along midline. Dorsal field with several inconspicuous setae (10 to 20) inserted in cavities.

Mandible. Anteromedially directed at an angle of 40-55° and enclosed in capsule. Mandibular bulge more or less distinctly raised, with 5-7 sensilla. Cuticle smooth to slightly sculptured or with longitudinal grooves. Mandibular tooth narrow or slightly widened, with or without spines.

Maxilla. Reduced and not distinctly protruding, fused to labium, often not clearly separated from labial area. Cuticle smooth or slightly wrinkled. Maxillary apex not projecting beyond mandible anteriorly. Vestige of palp inconspicuous, forming small bulge, sometimes very indistinct, located medially on ventral side of maxilla. Submaxillary groove more or less distinctly produced posteriorly to maxillary base.

Labium. Labial area flat, wider than long in midline or as wide as long, usually recognizable between maxillae but sometimes fused with them. Anteriorly delimited by mouth opening and posteriorly by birth opening. Cuticular surface smooth or slightly reticulated.

Mouth opening. Distinctly arcuate to nearly straight, sclerotized marginally.

Thorax and abdominal segment I. Pro-mesothoracic and meso-metathoracic borders distinct or indistinct, usually indicated by mesal furrows, often combined with pigmented stripes. Border between metathorax and abdomen usually formed by indistinct ridge or change in cuticular surface. Cuticle of thoracic segments on ventral side reticulate, often with scattered small and pigmented papillae. Dorsal side smooth or slightly wrinkled or reticulated. Prosternal extension either undifferentiated or indicated anteriorly by color pattern, in which case a swelling can be present or absent. Region of prosternal extension evenly connected to head on same plane (Fig. 25A ). Meso- and metathorax unmodified in shape, transverse. Setae or cuticular spines present on lateral region of abdominal segment I (Fig. 25E ).

Spiracles. Located on posterior ~ ⅓ of cephalothorax, slightly elevated, with anterolateral or anterodorsal orientation.

Diagnosis of male cephalotheca.

Differing from other genera in the following characters. Diameter of genae between maxillary base and compound eye at least 2 × as large as diameter of vestigial antenna. Distinct paired furrow of supra-antennal sensillary field absent. Cephalotheca always of elliptic shape (Fig. 27A ). Frontal fissure very distinct (Fig. 27D ). Maxilla prominent, at least 1.5 × longer than basally wide (Fig. 27E ).

Description of male cephalotheca.

Shape and coloration. In frontal view rounded laterally, elliptic, 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 arcuate in frontal view, prominent in lateral view. Clypeal sensilla mainly concentrated medially on clypeus. Frontal region slightly deformed by frontal impression (Fig. 27D ). Occipital bulge present (Fig. 27D ). Diameter of genae between maxillary base and compound eye very large, ~> 3 × as large as diameter of vestigial antenna.

Supra-antennal sensillary field. Kidney-shaped and bulging, medially delimited by frontal impression, lacking distinctly visible furrows.

Antenna. Of standard shape, small, with complete torulus and small plates (Fig. 27C ). Periantennal area not clearly delimited from supra-antennal sensillary field.

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

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

Maxilla. Distinct, prominent, entirely dark. Vestige of palp distinct.

Labium and hypopharynx. Distinct, dark, inserted between and below maxillae. Praementum and postmentum clearly separated by furrow. Hypopharyngeal protuberance not present.

Mouth opening. Distinctly arcuate but not well visible, covered by ventral labral field.

Phylogenetic relationships.

According to Benda et al. (2019) part of a clade of a New World origin, with Eupathocera Pierce as sister group.

Diversity and distribution.

Fourteen described species, restricted to the New World.

Hosts.

Various genera of Odynerini ( Vespidae : Eumeninae ).

Comments.

The genus Leionotoxenos was described by Pierce (1909) based on his suggestion that a new genus of Strepsiptera should be established if it utilizes a different host genus. No diagnosis or description was presented. It was later synonymized with Pseudoxenos ( Bohart 1937) and then with Paraxenos ( Kinzelbach 1971b). We restore Leionotoxenos from synonymy and classify it as a valid genus, based on the molecular phylogeny ( Benda et al. 2019, 2021) and morphological characters newly reported here. We classify the names Monobiaphila and Montezumiaphila as synonyms of Leionotoxenos .

Figures

Figure 24. Leionotoxenos bishoppi (Pierce), host, female, cephalothorax, photomicrographs A Monobia quadridens (Linnaeus) stylopized by female of L. bishoppi, lateral view B detail of host abdomen with adult female inside C ventral side of cephalothorax D dorsal side of cephalothorax.

Figure 25. Leionotoxenos bishoppi (Pierce), 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 detail of anterior border of cephalothorax, dorsal side. Abbreviations: a - vestigial antenna, at - antennal torulus, frp - frontal papillae, lehc - lateral extension of head capsule, paa - periantennal area, pst - prosternum (prosternal extension), ssf - supra-antennal sensillary field.

Figure 26. Leionotoxenos bishoppi (Pierce), 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: cll - clypeal lobe, fr - frontal region, ssf - supra-antennal sensillary field.

Figure 27. Leionotoxenos sp., male, cephalotheca, photomicrographs, SEM micrographs A frontal view B lateral view C vestigial antenna D frontal view E mouthparts. Abbreviations: fi - frontal impression, mx - vestige of maxilla, ob - occipital bulge.

Figure 29. Eupathocera luctuosae (Pierce), 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 detail of anterior border of cephalothorax, dorsal side. Abbreviations: a - vestigial antenna, at - antennal torulus, lehc - lateral extension of head capsule, paa - periantennal area, pst - prosternum, ssf - supra-antennal sensillary field, sssf - sensillum of supra-antennal sensillary field.