Deltoxenos impressus Benda & Straka, 2024

Benda, Daniel, Pohl, Hans, Beutel, Rolf & Straka, Jakub, 2024, Solitary folded-winged wasps of the genus Zethus Fabricius (Vespidae, Zethinae) parasitised by two new species of Strepsiptera on different continents, Journal of Hymenoptera Research 97, pp. 721-739 : 721-739

Deltoxenos impressus Benda & Straka sp. nov.

Type material.

Holotype. Kenya • 1 ♀; Mwingi, Kangonde vadi , 18 Apr. 2007; M. Halada leg.; OLML; host: Zethus favillaceus Walker, 1871 .

Paratypes. Kenya • 2 ♀; 1 ♀ + 2 empty male puparia; 1 ♀ + 1 male puparium; 1 ♀ + 1 male puparium + 2 empty male puparia; same locality and host as for holotype, 18 Apr. 2007; M. Halada leg.; OLML .

Diagnosis of female cephalothorax.

This species is easily distinguished from other representatives of the genus Deltoxenos by mandibles distinctly anteromedially directed (angle of 65 °) and by conspicuous impressions on the surface of the lateral extensions at the site of the reduced compound eyes. These impressions are best visible on SEM images (im; Fig. 6 A ) but also recognizable with a light microscope. The surface of the lateral extensions is slightly wrinkled or smooth in other species of Deltoxenos . The anterior head margin is rounded, and the clypeal lobe is merged with the head capsule, in contrast to Deltoxenos rueppelli (Kinzelbach, 1971) , where the clypeal lobe protrudes distinctly from the head capsule but is blunted on top. On the ventral side the clypeal area is very smooth and lacks sensilla (cl; Fig. 6 D ), whereas sensilla are present ventrally in Deltoxenos bidentatus (Pasteels, 1950) and D. rueppelli . In contrast to Deltoxenos bequaerti (Luna de Carvalho, 1956) , the cuticle of the thoracic segments on the ventral side is reticulate, with scattered inconspicuous or more distinct and pigmented papillae, mainly visible on the metasternum. In contrast, the thoracic segments on the ventral side are evenly scattered with conspicuous papillae in D. bequaerti .

Other characters that distinguish D. impressus sp. nov. from D. bidentatus and D. rueppelli : ventral field wider than long, elliptic, nearly circular versus more flattened and not nearly circular; dorsal field arcuate, slightly raised versus dorsal field distinctly arcuate and distinctly raised; mandible anteromedially directed at angle of 65 ° versus a maximum of 45 ° in D. rueppelli ; mandibular bulge distinctly raised, elongated, slightly curved laterally versus mandibular bulge slightly raised and anteriorly directed; cuticle of mandible completely smooth versus almost completely wrinkled.

Description of female cephalothorax.

Shape and colouration. Size of holotype cephalothorax: length 1.06 mm, width 0.9 mm. Cephalothorax variable in size but always distinctly longer than wide, length 0.9–1.06 mm, width 0.74–0.9 mm. Pro-mesothoracic and meso-metathoracic segmental border only slightly constricted laterally (Fig. 4 C, D ). Abdominal segment I not protruding laterally, corner below spiracles rounded. Anterior head margin rounded, not distinctly protruding from remaining head capsule. Thorax elongated, very slightly widening posteriorly. Cephalothorax with conspicuously contrasting light and dark colour pattern.

Head capsule. Ca 2 / 5 as long as entire cephalothorax including lateral cephalic extension. Colouration forming specific pattern with dark brown anterior part and pale lateral extensions. Surface of lateral extensions at site of reduced compound eyes smooth, with conspicuous impressions visible on SEM images (im; Fig. 6 A ). Clypeal area well delimited from labral area, arcuate, clypeal lobe merged with head capsule. Surface completely smooth with slightly more than 40 distinctly exposed sensilla on dorsal side (cls; Fig. 5 F ). Ventral side of clypeal area smooth and lacking sensilla (cl; Fig. 6 D ). Border between clypeal and frontal region indistinct but still present. Frontal region smooth (fr; Fig. 6 B ). Segmental border between head and prothorax indicated by distinct mesal furrow on dorsal side (sbhp; Fig. 6 B ) and by dorsal transverse stripe of frontal and occipital papillae (p; Fig. 6 B ). Head and prothorax distinctly separated by birth opening ventromedially (bo; Fig. 6 A ) and laterally by suture (sbhp; Fig. 6 A ).

Supra - antennal sensillary field. Completely smooth, with dispersed sensilla (Fig. 2 C, D ). Distinctly delimited by furrow on medial side (fssf; Fig. 6 B ), surface of supra-antennal sensillary field and frontal region with same sculpture.

Antenna. Preserved as poorly defined area, with several distinct rounded plates and an inconspicuous cavity (Fig. 5 C, D ). Antennal torulus reduced. Periantennal area expanded, smooth (paa; Fig. 5 C, D ). Border between antennal area and supra-antennal sensillary field indistinct.

Labrum. Ventral field wider than long, elliptic, nearly circular. Dorsal field arcuate, slightly raised, laterally narrower than medially, 6 × wider than long in midline (vlf, dlf; Fig. 6 C, D ). Dorsal field with 16 sensilla inserted in cavities.

Mandible. Mandibles anteromedially directed at angle of 65 °, enclosed in mandibular capsule. Mandibular bulge distinctly raised, elongated, slightly curved laterally, with several sensilla (mdb; Fig. 6 E, F ). Cuticle of mandible completely smooth. Mandibular tooth slightly curved, pointed apically, almost completely lacking spines (mdt; Fig. 6 E, F ).

Maxilla. Only slightly raised, almost fused with labial area (mx; Fig. 6 C ). Cuticle smooth, with longitudinal furrow. Apical maxillary region not projecting beyond mandibular apex. Basal part firmly connected with labium and not overlapping with mandible (mxb; Fig. 6 C ). Vestige of palp indistinct. Maxillary base distinctly produced anterolaterally as submaxillary groove. Space between prothoracic extension and head extended (sbhp, mxb; Fig. 6 A ).

Labium. Labial area quite indistinct between maxillae, delimited anteriorly by mouth opening and posteriorly by birth opening (lb; Fig. 6 C ). Flat, approximately as long as wide. Cuticular surface smooth.

Mouth opening. Widely arcuate, almost semicircular, sclerotised along margin (os; Fig. 6 C ).

Thorax. Pro-mesothoracic and meso-metathoracic borders visible ventrally as slightly imprinted mesal furrows (sbpm, sbmm; Figs 4 C , 5 A ). On dorsal side separated by conspicuous dark mesal furrows, distinctly contrasted with pale thoracic segments (sbpm, sbmm; Figs 4 D , 5 B ). Border between metathorax and abdomen indicated by ventral ridge on ventral side or indicated by change in colour and cuticular sculpture. Cuticle of thoracic segments on ventral side reticulate with scattered inconspicuous or more distinct pigmented papillae, mainly visible on metasternum. Prosternum conspicuously dark, mesosternum brown, and metasternum light brown. Prosternal extension undifferentiated. Dorsal side of thorax usually completely smooth, rarely with papillae on prothorax. All thoracic segments dorsally pale, but dark laterally. Meso- and metathorax transverse, rarely slightly elongated.

Abdominal segment I and spiracles. Setae and cuticular spines present on lateral region of abdominal segment I posterior to spiracle (Fig. 5 E ). Spiracles on posterior ~ 2 / 5 of cephalothorax slightly elevated, with anterolateral orientation. Cephalothoracic part of abdominal segment I below spiracles dark brown and medially light brown on both sides (asI, Fig. 4 C ).

Diagnosis of male cephalotheca.

This species is distinguished from other representatives of the genus Deltoxenos by a combination of the following characters: clypeal lobe distinctly arcuate in frontal view versus conspicuously bulging as in D. rueppelli ; shape of cephalotheca rounded in frontal view, very slightly flattened (Fig. 7 C ) versus more flattened in D. rueppelli ; frontal region with distinct impression versus impression not visible in D. rueppelli and D. bequaerti ; occipital bulge not protruding from elliptic shape of cephalotheca versus occipital bulge protruding in D. rueppelli and D. bequaerti .

Other characters that distinguish D. impressus sp. nov. from D. rueppelli : clypeal lobe as wide as mandible versus clypeal lobe distinctly wider than mandible; gena completely dark (gn; Fig. 7 C ) versus light brown.

Description of male cephalotheca.

Shape and colouration. In frontal view rounded, very slightly flattened, elliptic, length 0.6 mm, width 0.86 mm, in lateral view protruding anteriorly, pointed apically (Fig. 7 C, D ). Colouration predominantly dark with paler areas.

Cephalothecal capsule. Compound eyes visible, pale to dark, with dark individual cornea lenses. Clypeal lobe distinctly arcuate in frontal view, prominent in lateral view (cl; Fig. 7 C, D ). Clypeal area completely dark, clypeal sensilla indistinct. Clypeal lobe as wide as mandible.

Frontal region with paired furrow of supra-antennal sensillary field, distinct impression and slightly raised occipital bulge (ssf, fi, ob; Fig. 7 C ). Occipital bulge not protruding from elliptic outline of cephalotheca. Gena completely dark (gn; Fig. 7 C ). Diameter of genae between maxillary base and compound eye approximately 3 × larger than diameter of vestigial antenna.

Supra - antennal sensillary field. Dark, kidney-shaped and bulging, not delimited medially by distinct furrow (ssf; Fig. 7 ). Dark sensilla well visible.

Antenna. Of standard shape, dark, small, with small plates or sensilla and complete torulus (a; Fig. 7 C ). Periantennal area not clearly delimited from supra-antennal sensillary field. Small plates and sensilla present.

Labrum. Labral area distinct, slightly less dark medially. Dorsal field arcuate, with dispersed setae visible (dlf; Fig. 7 C ). Ventral field elliptic.

Mandible. Nearly medially directed (md; Fig. 4 E ). Colouration predominantly dark but slightly lighter medially. Distance between mandibles very distinctly exceeding mandibular length. Maxilla. Distinct, prominent, completely dark with inconspicuous paler spot anteriorly. Wide at base, approximately 2 × as wide as mandible (mx; Fig. 7 C ). Vestige of palp present, conspicuous (mxp; Fig. 7 C ).

Labium and hypopharynx. Labium distinct between and below maxillae, completely dark. Praementum and postmentum separated by furrow. Hypopharyngeal protuberance present but very indistinct (hyp; Fig. 7 C ). Mouth opening well visible, not covered by ventral labral field, distinctly arcuate.

Etymology.

From the Latin substantive impressio, meaning an impression or hole. The specific epithet refers to conspicuous impressions on the lateral extensions of the female cephalothorax. Adjective.

Figures

Figure 2. Holotype of Eupathocera zethi Benda & Straka, sp. nov., ♀ (NMPC), SEM micrographs of cephalothorax A ventral side B dorsal side C right vestigial antenna, dorsal side D left 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: asI – abdominal segment I, fr – frontal region, lehc – lateral extension of head capsule, mst – mesosternum, mtst – metasternum, paa – periantennal area, pra – plate of vestigial antenna, pst – prosternum (prosternal extension), sbmm – segmental border between mesothorax and metathorax, sbpm – segmental border between prothorax and mesothorax, ssf – supra-antennal sensillary field.

Figure 4. Deltoxenos impressus Benda & Straka, sp. nov., host, female cephalothorax A Zethus favillaceus Walker, 1871 stylopised by D. impressus sp. nov., lateral view B detail of host abdomen of Z. favillaceus, with female cephalothorax C – D holotype of D. impressus sp. nov., ♀ (OLML) from Z. favillaceus C ventral side of cephalothorax D dorsal side of cephalothorax. Abbreviations: asI – abdominal segment I, cll – clypeal lobe, csI – constriction of abdominal segment I, lehc – lateral extension of head capsule, mst – mesosternum, mtst – metasternum, pst – prosternum (prosternal extension), sbhp – segmental border between head and prothorax, sbma – segmental border between metathorax and abdomen, sbmm – segmental border between mesothorax and metathorax, sbpm – segmental border between prothorax and mesothorax, sp – spiracle.

Figure 5. Holotype of Deltoxenos impressus Benda & Straka, sp. nov., ♀ (OLML), SEM micrographs of cephalothorax A ventral side B dorsal side C right vestigial antenna, dorsal side D left 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, asI – abdominal segment I, cls – clypeal sensillum, lehc – lateral extension of head capsule, mst – mesosternum, mtst – metasternum, paa – periantennal area, pst – prosternum (prosternal extension), sbmm – segmental border between mesothorax and metathorax, sbpm – segmental border between prothorax and mesothorax.

Figure 6. Holotype of Deltoxenos impressus Benda & Straka, sp. nov., ♀ (OLML), SEM micrographs of cephalothorax 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: bo – birth opening, cl – clypeal area, dlf – dorsal labral field of labral area, im – impression, lb – labial area, md – mandible, mdb – mandibular bulge, mdt – mandibular tooth, mx – vestige of maxilla (maxilla), mxb – maxillary base (at mandible base), os – mouth opening, p – papilla, sbhp – segmental border between head and prothorax, vlf – ventral labral field of labral area.

Figure 7. Deltoxenos impressus Benda & Straka, sp. nov., host, male cephalotheca A Zethus favillaceus Walker, 1871 stylopised by D. impressus sp. nov., lateral view B detail of host abdomen of Z. favillaceus, with male cephalotheca C – D paratype of D. impressus sp. nov., ♀ (OLML) from Z. favillaceus C ventral side of cephalothorax D dorsal side of cephalothorax. Abbreviations: a – vestigial antenna, cl – clypeal area, coe – compound eye, dlf – dorsal labral field of labral area, fr – frontal region, gn – gena, md – mandible, mx – vestige of maxilla, mxp – vestige of maxillary palp, ob – occipital bulge, pom – postmentum, prm – praementum, ssf – supra-antennal sensillary field, vlf – ventral labral field of labral area.