Xenogaster pseudonuda Pires-Silva 2023, sp. nov.
Creators: name: Pires-Silva, Carlos M.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Xenogaster
Xenogaster pseudonuda

description: 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.
description: Published as part of Pires-Silva, Carlos M., 2023, Two new species of the termitophilous rove beetle genus Xenogaster Wasmann from Brazil (Staphylinidae, Aleocharinae, Corotocini), pp. 247-264 in Zootaxa 5239 (2) on pages 248-254, DOI: 10.11646/zootaxa.5239.2.4, http://zenodo.org/record/7624247