Euryachen seuzei, Pires-Silva, 2023

Pires-Silva, Carlos M., 2023, Euryachen seuzei a new genus and species of Placusini (Coleoptera: Staphylinidae Aleocharinae) from Brazil, Zootaxa 5230 (4), pp. 467-477 : 469-473

Euryachen seuzei gen. et sp. nov.

Material Examined. Holotype. J MZSP 21308 : BRAZIL. São Paulo: Peruíbe , 27–29.IX.1984. Exp. MZUSP col., in EtOh 70% ( Figs. 1 , 3–5 , 7 )

Paratypes. All paratypes are in EtOH 70%, have the same data as holotype, and are cataloged as follows : 9 ♀ MZSP 21309 , MZSP 21313 , MZSP 21315 , MZSP 21316 , MZSP 21317 , MZSP 21318 , MZSP 21319 , MZSP 21321 , MZSP 21322 ; 5 J MZSP 21310 , MZSP 21311 , MZSP 21312 , MZSP 21314 , MZSP 21320 .

Other material. Additional material has the same data as holotype: 2 J and 1 ♀ ( MZSP) dissected on slides ; 2 adults with undetermined sex.

Diagnosis: Same as for the genus, with the inclusion of color data. Overall body light ferruginous: head and thorax slightly darker; legs and abdominal segment IX light yellow, tergites VII and VIII reddish-yellow on males and lighter on females.

Description

Length: 2 mm –2.2 mm ( Figs. 1–8 )

Head ( Fig. 9 ). Spherical, about 1.3 times as wide as long; microsetae sparse and uniformly distributed on head surface and ventral regions. Antenna ( Fig. 11 ) with 11 antennomeres, scape elongated; antennomeres I–III subcylindrical, longer than wide; IV quadrate, the shorter; V–VI subequal in length, slightly wider than long; VII–X distinctively transverse; XI conical. Labrum ( Figs. 12 , 38 ) membranous and broadly rounded, setae p1-p2/m1-m2/d1-d2 present, with a small rounded lobe bearing a-sensilla. Epipharyngeal region with a longitudinal irregular band of pores, laterally bordered by a longitudinal curved row of scale-like structures. Mandibles ( Figs. 13 , 37 ) asymmetrical. Dorsal molar area bearing seven transverse rows of large denticles, denticles of each row decreasing basad; ventral region smooth, without denticles. Right mandible with a distinct subapical tooth, absent on left mandible, which has broader apex. Dorsal sensory pores present, transversally distributed. Prostheca short. Maxilla ( Fig. 14 ) slender, with galea slightly longer than lacinia; lacinia broad, with a longitudinal row of lacinial teeth, occupying almost ½ of the total length of lacinia; teeth longest at apex. Galea with a patch of four spines at apex. Maxillary palpi ( Fig. 15 ) 4-articulated: palpomere 1 short, transverse; 2, subcylindrical, broader at apex; 3, suboval; and 4, and subulate. Labium ( Figs. 16 , 39 ). Labial papi 2-articulated, short; palpomere 1 broad, longer than palpomere 2; 2 cylindrical. Setae a, b, d, f, h present. Ligula ( Figs. 16 , 39 ) short and broadly rounded; with small sensitive pores on surface. Mentum-submentum distinct. Mentum ( Figs. 10 , 40 ) transverse, trapezoidal, anterior margin slightly emarginate, posterior margin almost straight and lateral margins diverging posteriorly. Apical, preapical and proximal setae present, symmetrically distributed. Gula long, occupying about 2/3 of head length. Gular sutures parallel.

Prothorax. Pronotum ( Fig. 17 ) transverse, about 1.2 times as wide as long, slightly narrower than elytra; anterior margin straight with short, almost indistinct, rounded angles; posterior margin broadly and weakly arcuate; with distinct posterior angles. Uniformly covered with short and sparse bristles. Hypomera distinct. Prosternum ( Fig. 18 ) like a distinct transverse and trapezoidal plate. Meso- metathorax ( Fig. 19 ) weakly sclerotized, with sparse and short bristles along the postero-lateral margins. Metendesternite Y-shaped; basal stalk narrow, with a digitiform projection between furcal arms; furcal arms reaching the level of mesocoxal cavities. Scutellum transverse. Metanotum ( Fig. 20 ) membranous, slightly shorter than metathorax. Elytra ( Fig. 21 ) elongated; almost reaching anterior margin of tergite III; anterior margin forming rounded angles; posterior margin individually slightly sinuose. Short bristles uniformly distributed along elytral surface. Legs. Procoxae ( Fig. 22 ) transverse, flattened; mesocoxae ( Fig. 24 ) rounded; metacoxae ( Fig. 26 ) somewhat triangular, flattened; ventrally covered with bristles. Tibia slightly longer than femur; bearing thick spine-like bristles. Protibia bearing a pair of tibial spurs, meso- and metatibia each with a single tibial spur. Tarsal formula 4-4-5 ( Figs. 23, 25, 27 ). Pro-, meso- and metatarsi each with two unciform claws.

Abdomen parallel-sided, narrowed at apex. Tergites and sternites separated by two pairs of narrow paratergites on abdominal segments III–VII. Tergites II–VII coarsely covered with bristles. Tergite I indistinct; tergites II–VI transverse; males with tergite V ( Figs. 28 , 41 ) bearing 7–9 spine-like bristles centered and thick bristles on the postero-lateral margins of tergite VII. Tergite VII ( Figs. 30–31 , 43–44 ) broader at base, slightly longer than tergite VI. Tergite VIII ( Fig. 32 ) subquadrate, with same chaetotaxy pattern for males and females. Tergite IX broad, with longitudinal rows of bristles. Tergite X ( Fig. 33 ) broad, quadrate; with a dense and subquadrate patch of setae. Aedeagus. Median lobe ( Fig. 34 ) elongated, piriform, weakly rounded at base. Lateral lobes ( Figs. 34–35 ) with a long and very narrow distal segment, bearing three short bristles. Spermatheca ( Fig. 36 ) spherical and sclerotized.

Biologica notes: The material studied was collected in trunks in a newly felled forest. Adults of Euryachen seuzei were collected under bark, together with larvae of Glyptoma Erichson. Both are together in the sample (MZSP 570). Studying more material of the same locality, other samples were found with both taxa mixed: in one (MZSP 570), larvae of Glyptoma were together with adults of Placusini , and in another (MZSP 590), some Aleocharinae larvae ( Homalotini ) were together with Glyptoma adults.

These observations let to conclude that adults and larvae of Placusini and Glyptoma can share the same subcortical habitat, and although Euryachen larvae were not found, one cannot rule out the possibility that they also live with the adults.

Etymology. The specific epithet “ seuzei ” is a noun in the genitive case in honor of my grandfather, José Pires Ferraz. A kind-hearted man who prioritizes his family above all else. “Seu Zé” is a common nickname in Brazil for “José”, and also how he is called by his family and friends.

Distribution. Brazil — São Paulo: Peruíbe.

Figures

FIGURES 1–2. Euryachen seuzei gen. et sp. nov. habitus lateral. 1, holotype; 2, paratype (female). Scale bars = 0,55 mm

FIGURES 3–6. Euryachen seuzei gen. et sp. nov. habitus dorsal. 3–5, holotype, detail of tergite V (4) showing the spine-like bristles on male and tergite VII (5), showing the thicker bristles near lateral margins; 6, paratype (female). Scale bars = 0,5 mm (3, 6)

FIGURES 7–8. Euryachen seuzei gen. et sp. nov. habitus ventral. 7, holotype; 8, paratype (female). Scale bars = 0,5 mm

FIGURES 9–21. Euryachen seuzei gen. et sp. nov. 9, head, venral view; 10, mentum-submentum, ventral view; 11, antenna; 12, labrum, dorsal view; 13, mandibles, dorsal view; 14, maxilla, dorsal view; 15, maxillary palpi 2–4, dorsal view; 16, labium, ventral view; 17, pronotum, dorsal view; 18, prosternum, ventral view; 19, meso- and metaventrite, ventral view; 20, meso- and metanotum, dorsal view; 21, elytra, dorsal view. Scale bars = 0,25 mm (13); 0,125 mm (11, 18, 19); 0,08 mm (17, 20); 0,075 mm (9, 15); 0,05 mm (10, 21); 0,03 mm (14); 0,025 mm (12, 16).

FIGURES 37–40. Euryachen seuzei gen. et sp. nov. Illustrative schemes of mouthparts. 37, right mandible (dorsal aspect); 38, labrum, dorsal; 39, labial complex, ventral view; 40, mentum, ventral view. lg: ligula, ds: distal setae, ap: apical setae; pa: preapical setae; px: proximal setae.

FIGURES 22–36. Euryachen seuzei gen. et sp. nov. 22, front leg, lateral view; 23, front tarsus, lateral view; 24, middle leg, lateral view; 25, middle tarsus, lateral view; 26, hind leg, latral view; 27, hind tarsus, lateral view; 28, tergite V of male, dorsal view; 29, tergite V of female; 30, tergite VII of male; 31, tergite VII of female; 32, tergite VIII; 33, tergite X; 34, aedeagus, dorsal view; 35, detail of lateral lobe; 36, spermatheca; ts: tibial spur. Scale bars = 0,1 mm (32); 0,08 mm (30, 31); 0,075 mm (22, 24, 26, 28, 29); 0,05 mm (33, 34); 0,025 mm (23,25, 35, 36); 0,02 mm (27).

FIGURES 41–44. Euryachen seuzei gen. et sp. nov. Tergite V of male (41) and female (42); tergite VII of male (43) and female (44). Ventral view.