Xenogaster pseudonuda Pires-Silva, 2023

Pires-Silva, Carlos M., 2023, Two new species of the termitophilous rove beetle genus Xenogaster Wasmann from Brazil (Staphylinidae, Aleocharinae, Corotocini), Zootaxa 5239 (2), pp. 247-264 : 248-254

Xenogaster pseudonuda Pires-Silva sp. nov.

( Figs. 1–46 , 92, 94, 96 , 97 , 99 , 100 )

Type material. HOLOTYPE, male. BRAZIL: “Peruíbe—S„o Paulo ; 28–30.VI.1982; Vanin, S. A. & Costa C., cols., in alcohol 70%” ( MZUSP 21360 ) . PARATYPE, 1 female, same data as holotype (dissected on slides) ( MZUSP 21361 ) .

Male: Length ~3.4 mm ( Figs. 1–3 )

Female: Length ~3.6 mm ( Figs. 4–6 )

Diagnosis. Similar to Xenogaster subnuda Seevers, 1957 through the general aspect but distinguished by slightly convex frons, deflexed clypeus, and differences in male genitalia ( Figs. 43–46 ). Differs also by the body brownish yellow, physogastric with membranous areas between tergites and sternites yellowish white.

Head ( Fig. 7 ). Slightly longer than wide, parallel at 2/4 median and gradually narrowed anteriad and posteriad, forming rounded posterior angles; dorsal surface of head finely punctuate; frons slightly projected, broadly and weakly arcuate. Clypeus membranous and transverse; slightly deflexed in front of antennal fossae producing a transversal carina between posterior margins of antennal insertions. Gula long, with almost 2/3 of total head length, fused to submentum; gular sutures diverging near the posterior region of the head.Antennae ( Figs. 12 , 100 ) cylindrical with 11 antennomeres; antennomere II longer than wide, narrowed at base, subtriangular, as long as antennomeres IV - X; antennomeres III–IX subquadrate slightly decreasing in length apicad; couples of antennomeres subequal in length: II–III; IV–V; VI–VII; VIII–IX. Antennomeres III and XI bearing one pair of coeloconic sensilla each. Labrum ( Fig. 11 ) slightly wider than long, membranous, with two long bristles on posterior margin. Mandibles ( Fig. 8 ) symmetrical; each with an apical and subapical tooth; broader at base and slightly narrowed and curved apicad; prostheca membranous, occupying almost the whole mesal length (in fig. 8, indicated by red arrows); dorsal sensitive pores near base. Maxilla ( Fig. 9 ) with cardo transverse, subtriangular, rounded laterally; stipes rectangular, longer than wide, almost the same size of galea; lacinia and galea band-like and arcuate, similar in length; lacinia narrow, with a distal comb of bristles across inner margin; distal lobe of galea bearing a thick comb of bristles. Maxillary palpi 4-articulated, arcuated; palpomere I reduced, almost indistinct, ring-like; II elongate, curved, subcylindrical, dilated at apex and gradually narrowing at base; III elongate, oval, slightly narrower than previous, with sparse long bristles; IV elongate, narrow and slightly narrowed apicad. Labial palpi ( Fig. 10 , 97 ) 3-articulated; palpomere I elongate, cylindrical; II almost as long as wide, about ½ of the length of palpomere I, with setulae e and f present; III elongate, cylindrical, narrower and longer than previous, with apical sensilla at apex (as). Ligula ( Fig. 97 ) prominent and bilobed, each lobe (lb) with surface somewhat scale-like; with a digitiform projection between lobes, bearing two apical spiniform sensilla (asp). Prementum membranous, short, band-like. Mentum fused to submentum, with lateral margins straight, anterior and posterior angles divergent; a pair of apical bristles (ap) on each edge of anterior margin, and a transverse row of short bristles between the apical ( Fig. 99 ). Postmentum fused to gula ( Fig. 13 ).

Prothorax ( Fig.18 , 35–38 ).Pronotum subquadrate, with anterior and posterior margins parallel; slightly elevated on its posterior region, which is slightly arcuate with rounded angles. Pronotal disc broadly and deeply impressed; impression rosacea-like formed by geometric irregular petals, marginated by micropunctuation, each with a short stout bristle. Brownish-yellow with lateral margins darker; strongly punctate, giving an impression of a different texture. Pronotum irregularly grooved longitudinally forming elevations; lateral margins of pronotum rounded and downwardly directed; three bristles longitudinally distributed on each side of lateral margins. Meso- metathorax ( Fig. 14 ) weakly sclerotized, bearing a pair of bristles symmetrically placed on anterior margin, lateral margins finely punctuated (in fig. 14, punctuate area marked by arrows). Metendosternite ( Fig. 16 ) Y-shaped, basal stalk bilobed at base; fucal arms parallel, not reaching mesocoxal margins. Scutellum ( Fig. 15 ) transverse and trapezoidal with rounded angles. Metanotum membranous, fused to metasternum; longer than metanotum. Wings reduced to stubs ( Fig. 15 ). Elytra ( Figs. 17 , 39–42 ) elongate, slightly wider on posterior region, forming rounded angles; clear ferruginous, outer margins longer and darker; densely punctuated, with a grainy appearance; anterior and posterior margins declivous and convergent; inner margins separated completely from behind scutellum to apices; anterior margin with a single long bristle near apex; rosacea-like formed by scales-like intertwined with short bristles. Legs ( Figs. 19–21 ). Procoxae longer and subtrapezoideal, mesocoxae oval, and metacoxae triangular. Femora elongated and cylindrical, with inner margins almost straight; tibia slightly narrower and almost the same length as the femur, covered with short bristles along the whole surface; mesotrochanter slightly longer than protrocanter; metatrochanter the longest, bearing a single long bristle ( Fig. 20 ). Tarsi ( Figs. 22–24 , 92, 94, 96 ); tarsal formula 5-5-5, with 4 th and 5 th tarsomeres almost fused, but presenting a clear line of division between them– (In figs. 92, 94, 96, division line indicated by arrows); first tarsomere of pro- and mesotarsus almost of the same length; first tarsomere of metatarsus longer than the metatarsomeres 2–5 combined; last tarsomere with two unciform claws and a dentiform projection between claws.

Abdomen physogastric with membranous wide areas among sclerites. Tergites and sternites separated by two pairs of paratergites in abdominal segments III–VI; bristles of tergites always on sclerites; inner paratergites sclerotized, subquadrate, outer paratergites narrow. Segment I membranous, reduced, fused to metanotum; segment II with a reduced tergite, shorter than tergite III, and anterior margin emarginate at middle; second sternite transverse, plate-shaped; tergites III–V rectangular; tergite III with anterior margin slightly emarginate at middle; tergites III– VI with one row of bristles; tergite VII ( Fig. 25 ) band-like and subtrapezoideal, with posterior margin emarginate; anterior margin straight, with one pair of rounded glandular reservoirs, each widely separated; one row of 4 long bristles in the medial region; finely punctuated in the whole surface; posterior margin marginate by fringe of fine bristles. Tergite VIII ( Fig. 27 , female; Fig. 30 , male) subquadrate, wider than long; anterior margin straight; lateral margins rounded; posterior margin slightly sinuose; one transversal row of four bristles near posterior margin, symmetrically distributed. Sternite VIII ( Fig. 26 , female; Fig. 31 , male) with basal margin roundly emarginated, continuous laterally by sclerotized extension on females; and forming short angles in male; transversal row of six bristles near posterior margin symmetrically distributed; sternite IX represented by a pair of hemisternites laterally attached to tergite IX. Tergite IX subtriangular, with two long bristles in a longitudinal row parallel to lateral margin; male sternite IX ( Fig. 28 ) represented by three long extensions (apodemes). Tergite X band-like, fore angles rounded, covered with short bristles and with two transversal rows of long bristles symmetrically distributed parallel to anterior margin. Aedeagus ( Figs. 29 , 43 ) piriform, basal capsule broad; apical lobe narrowing apicad; lateral lobes ( Fig. 45 ) with distal segment short, with four short bristles on apex; medial segment broad and proximal segment narrow and elongate. Spermatheca sclerotized, stem elongated; capsule dilated at apex ( Fig. 34 ).

Type-locality. Brazil. S„o Paulo: Peruíbe

Host. Beetles were collected inside a nest of Nasutitermes sp. in a fallen tree trunk (L. R. Fontes private collection, pers. comm.).

Etymology. The specific epithet “ pseudonuda ” is an allusion to the similarity that the new species shares with Xenogaster subnuda .

Figures

FIGURES 97. Labial complex of Xenogaster pseudonuda sp. nov. Abbreviations = as: apical sensilla; asp: apical spiniform sensilla; ds: distal seta of prementum; lb: lobe; lg: ligula.

FIGURE 100. Sensilla on antennomere III of Xenogaster pseudonuda sp. nov.

FIGURES 1–3. Xenogaster pseudonuda sp. nov., holotype male. Habitus (elytra missing). 1, lateral; 2, ventral, 3, dorsal. Scale bars = 0,85 mm.

FIGURES 4–6. Xenogaster pseudonuda sp. nov., paratype female. Habitus.4, lateral; 5, ventral, 6, dorsal. Scale bars = 0,9 mm.

FIGURES 7–34. Xenogaster pseudonuda sp. nov. 7, head, ventral view; 8, mandibles, dorsal view; mandibular prostheca indicated by arrows; 9, maxilla; 10, labium, dorsal view; 11, labrum, dorsal view; 12, antenna; 13, postmentum, ventral view; 14, meso- and metaventrite, ventral view; 15, scutellum, meso- and metanotum, and abdominal tergite I, dorsal view; 16, endosternite; 17, elytra, dorsal view; 18, prosternum; 19. front leg; 20, hind leg; 21, middle leg; 22, front tarsus; 23, middle tarsus; 24, hind tarsus; 25, tergite VII; 26, sternite VIII (female); 27, tergite VIII (female); 28, tergite IX–X (male); 29, aedeagus, dorsal view; 30, tergite VIII (male); 31, sternite VIII (male); 32, tergite IX–X (female); 33, tergite X (male), 34, spermatheca. Scale bars = 0,025 mm (8, 9, 10, 11); 0,05 mm (22, 23, 24, 32, 33, 34); 0,06 mm (13); 0,075 mm (17, 18, 25, 26, 27, 30, 31); 0,1 mm (7, 12, 14, 15, 16, 19, 20, 21, 28, 29).

FIGURES 35–38. Xenogaster pseudonuda sp. nov. 35, pronotum (dorsal); 36, detail of lateral margins; 37, microsetae on pronotal disc; 38, details of outer border of lateral margin. White arrows point to a fallen bristle. Scale bars = 3 µm (35), 10 µm (36, 37, 38).

FIGURES 39–42. Xenogaster pseudonuda sp. nov. 39, elytra (dorsal); 40, detail of apex of anterior region; 41, detail of small bristles near lateral margins; 42, detail of long bristle of elytra. Scale bars = 3 µm (42); 10 µm (40, 41); 30 µm (39).

FIGURES 43–46. Illustrative schemes showing the differences between the genitalia of Xenogaster pseudonuda sp. nov and X. subnuda. 43, aedeagus of X. pseudonuda (dorsal view); 44, aedeagus of X. subnuda (dorsal view), 45, lateral lobe of X. pseudonuda; 46, lateral lobe of X. subnuda. Abbreviations = al: apical lobe; LL: lateral lobe; bc: basal capsule; px.s.: proximal segment; md.s.: medial segment; dt.s.: distal segment.

FIGURES 91–96. Metathoracic legs. 91, 93, Xenogaster kypomoleia sp. nov.; 92, 94, X. pseudonuda sp. nov; 95, detail of last tarsomeres of X. kymopoleia and 96, X. pseudonuda. Division line of 4th and 5th tarsal segment indicated by arrow. Scale bars = 100 µm (91, 92); 20 µm (93, 94); 10 µm (95, 96).

FIGURES 98–99. 98, postmentum of Xenogaster pseudonuda sp. nov; 99, postmentum of Xenogaster kymopoleia, sp. nov. Abbreviations = ap: apical bristles.