Scopaeus saotomensis Frisch, 2024

Frisch, Johannes, Turner, Clive R. & Aristophanous, Marios, 2024, Scopaeus saotomensis spec. nov., a flightless rove beetle from the Island of São Tomé (Coleoptera: Staphylinidae: Paederinae: Lathrobiini) - Isolation and adaptation in a dark, humid, tropical forest environment, Soil Organisms 96 (2), pp. 69-78 : 73-75

Scopaeus saotomensis Frisch , spec. nov.

( Figs 1–10 )

Type specimen: Holotype ♂, República Democrática de São Tomé e Príncipe, São Tomé, Lagoa Amelia (0°16’30.7”N, 6°35’31.2”E), 1475 m, 18.- 26.1.2018, leg. Aristophanous, Lima, Miles & Turner.

Description: Habitus and coloring as in Fig. 1 . Body colour unicolorous medium brown with maxillary palpi and legs slightly lighter brown; antennae with scapus and pedicellus medium brown; antennae from blackish median segments gradually lighter towards light brown segment 11. Body surface with short, decumbent pubescence, coarsely and densely punctate with punctures of elytra about twice the diameter of punctures of head and pronotum; microreticulation absent. Head subcircular with posterior angles broadly rounded towards slightly concave posterior margin. Macrophthalmous with eyes about 0.7 times as long as tempora. Antennal segments elongate; penultimate segment 1.2 times as long as wide. Micropterous, with elytra short and narrow, about 0.7 times as long as pronotum and 0.9 times as wide as head, fused at suture, with broadly rounded humeral angles and shallow, transverse depression in anterior half; metathoracic wings vestigial. Mesotibia strongly thickened. Stridular file contiguous with submarginal ridge of metaventrite, occupying about anterior two thirds of submarginal ridge, and curved dorsad at posterior end ( Figs 2, 3 ); cluster of six, subparallel plectral ridges situated in dorsal half of posterior surface of mesofemur and touching dorsal femoral margin; plectral ridges almost straight and parallel to dorsal femoral margin, becoming less prominent and shorter from dorsal femoral margin towards middle of mesofemoral width ( Fig. 4 ). Metakatepisternal processes longer than wide, apically acute. Abdominal tergites III-VI with deep, transverse, basal depression in about proximal half of sternite length with scabrous surface sculpture clearly separated from regularly punctate distal half of tergites ( Figs 1 , 2 ); abdominal sternites IV-VI with deep, transverse, basal constriction ( Figs 1 , 2 ); palisade fringe absent from abdominal tergite VII. Total body length 3.6 mm; forebody length 1.9 mm.

Male: Abdominal sternite VII posterior of transverse basal ridge with shallow depression in median third of width, triangular emargination in median third of posterior tenth and short, narrow, ventroposteriad pointing, distally widened, median process with truncate end projecting from posterior emargination ( Fig. 8 ). Abdominal sternite VIII in about posterior half with strong, transverse depression convexly curved towards transverse basal ridge, in posterior ninth with short, wide, bisinuate emargination ( Fig. 9, 10 ).

Aedeagus ( Figs 5–7 ) about 0.6 mm long. Apical lobes and dorsal lobe not distinguishable in the microscopic image, seemingly fused to asymmetrical, narrow, somewhat dextrad curved distal lobe with round apex and large, irregularly convex, ventrodextral, lobiform enlargement at base. Flagellum long, reaching distal fourth of length of distal lobe, slightly running left in proximal half but in distal half strongly curved dextrad with bidentate end owing to sinistral widening over entire length of flagellum ending in long, thin, second apical tooth; additional, apicad pointing tooth seemingly projecting in middle of length of flagellum. Ventral lobe short, with thin, acutely ended, hook-shaped spine pointing proximad. Lateral lobes asymmetrical, each bearing group of long, ventrally pointing setae; dextral lateral lobe reduced; sinistral lateral lobe lobiform, projecting from phallobase. Apical portion of phallobase with additional, isolated, ventral bristles. Median foramen somewhat transverse, limited laterally by strongly sclerotised, vestigial parameres.

Female unknown.

Phylogeny: The asymmetical apical portion of the aedeagus with dextrad curved distal lobes and flagellum, lateral lobes of unequal length and the long flagellum identify Scopaeus saotomensis as belonging to the S. crassipes lineage of the S. gracilis species group ( Frisch et al. 2002: 37, 39), which is very speciose in the tropical and subtropical Old World.

Distribution: Due to its flightlessness, Scopaeus saotomensis is probably endemic to the island of São Tomé in the Gulf of Guinea.

Habitat and collecting method: The holotype of Scopaeus saotomensis was captured in a pitfall trap set near the top of the southern ridge of Lagoa Amélia in an area of rainforest above the crater lake at an elevation of 1475 m asl ( Fig. 11 ). The unlidded and unbaited pitfall trap comprised of a plastic 0.5 L yoghurt pot set in the ground with the edge below the soil surface and partially filled with 100 ml of 50 % propan-1,2-diol and finished off with a generous shake of extra hot chilli powder to deter mammals. The trap was set for a period of six days. The rainforest was very wet and extremely humid, characteristic of the montane forests of São Tomé and locally enhanced by the super-humid environment of the Lagoa Amélia area.

Etymology: With the epithet saotomensis (adjective, Latin, composed of the geographic name São Tomé and the suffix –ensis, which indicates the geographical origin) reference is made to the island of São Tomé, the area of discovery for the new species.

Figures

Figure 1. Habitus of Scopaeus saotomensis, holotype, República Democrática de São Tomé e Príncipe, São Tomé, Lagoa Amelia.

Figures 2–4. Scopaeus saotomensis, lateral aspect exhibiting basal depressions of abdominal tergites (upper arrows), basal constrictions of abdominal sternites (lower arrows), and stridular file on dorsolateral surface of metaventrite (2); enlarged view of stridular file (3); plectral ridges on posterior surface of base of mesothoracic leg (4).

Figures 5–10. Scopaeus saotomensis, holotype, República Democrática de São Tomé e Príncipe, São Tomé, Lagoa Amelia; aedeagus in lateral (5), ventral (6), dorsal (7) view;abdominal sternite VII (8); abdominal sternite VIII in ventral (9) andlateral (10)view.Abbreviations: dl – distal lobes (apical lobes and dorsal lobe not distinguishable), f – flagellum, ll – lateral lobes, mf – median foramen, mtf – median tooth of flagellum, p – parameres, sl – groups of setae of lateral lobes, sp – setae of phallobase, vdl – ventrodextral, lobiform enlargement of distal lobes, vl – ventral lobe.

Figure 11. The pitfall trap (arrow) in situ at Lagoa Amélia illustrating the exact collecting spot for Scopaeus saotomensis.