Scydmaenus alatus Nietner 1856
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Scydmaenus
Scydmaenus alatus

description: Scydmaenus (incertae sedis) alatus Nietner
(Figs 18, 35–36)
Scydmaenus alatus Nietner, 1856: 543.
Scydmaenus (Scydmaenus) alatus Nietner; Franz, 1982: 130.
Type material. Lectotype (here designated): ♂, three labels: “ Ceylon / Nietner..s” (white, printed and handwritten, text in black frame], QR code label with collection number 8190, and newly added “ SCYDMAENUS / (i. s.) / alatus Nietner, 1856 / LECTOTYPUS / P. Jałoszyński, 2025 ” (MIZ). Paralectotypes (2 exx.): 1 ♂, 1 ♀, with white printed copies of locality label and identification labels with “PARALECTOTYPUS” (MIZ).
Revised diagnosis. Antennomere 9 only slightly enlarged, so that antennal club appears as dimerous; pronotum lacking antebasal pits; aedeagus in dorsal view elongate triangular, broadest shortly distad base, from the widest site narrowing distad with nearly straight lateral margins and narrowly rounded apex, dorsal ostium flanked by pair of high ridges visible in lateral view in distal half.
Redescription. Body of male (Fig. 18) strongly elongate and weakly convex, light brown; setae distinctly lighter than cuticle; BL 1.20 mm.
Head broadest across small and finely faceted eyes weakly projecting from head silhouette, HL 0.20 mm, HW 0.23 mm; frontal and vertexal regions confluent, weakly convex, vertex not impressed posteromedially; supraantennal tubercles weakly elevated. Punctures on frons and vertex fine and inconspicuous; setae sparse, short and recumbent. Antennae slender, with trimerous clubs, but antennomere 9 only slightly enlarged, so that clubs appear as dimerous, AnL 0.60 mm; antennomere 1 and 2 strongly elongate, 3–6 elongate, 7 about as long as broad, 8 weakly transverse, 9 distinctly transverse, 10 about as long as broad, 11 indistinctly broader than 10, slightly longer than 9–10 combined, about 1.8 times as long as broad.
Pronotum oval, broadest between middle and anterior third; PL 0.35 mm, PW 0.30 mm; anterior margin strongly rounded and confluent with lateral margins, which are anteriorly strongly rounded and posteriorly nearly straight; posterior corners obtuse-angled and blunt; posterior margin weakly arcuate; base lacking pits. Punctures on pronotal disc similar to those on frons and vertex; setae short, moderately dense and suberect.
Elytra together oval, broadest slightly anterior to middle; EL 0.65 mm, EW 0.45 mm, EI 1.44; humeral calli not elevated, basal impressions virtually absent; elytral apices separately rounded. Punctures and setae similar to those on pronotum.
Legs long and slender, protarsi broadest proximally and distinctly narrowing distad.
Metathoracic anapleural sulcus complete.
Aedeagus (Figs 35–36) strongly elongate; AeL 0.28 mm; median lobe in dorsal view broadest near base and strongly narrowing distad, lateral margins in distal 2/3 very slightly sinuate, subapical region with long lateral setae; in lateral view a pair of longitudinal ridges flanking ostium strongly elevated and occupying entire distal half of aedeagus, apex both in dorsal and lateral view narrowly rounded.
Female. Externally similar to male, but with indistinctly slenderer protarsi. BL 1.25 mm; HL 0.23 mm, HW 0.25 mm, AnL 0.60 mm; PL 0.33 mm, PW 0.31 mm; EL 0.70 mm, EW 0.45 mm, EI 1.56.
Distribution. Sri Lanka, near Colombo.
Remarks. The type series of this species consisted of four specimens mounted on a single card. After remounting, two of them were found to be males, and two are females. Two males and one female belong to one species, characterized by a strongly enlarged antennomeres 10 and 11, but weakly enlarged antennomere 9, and therefore their clubs can be described as dimerous. One female is clearly not congeneric; its antennal clubs are trimerous. Nietner (1856) noticed this difference and explained that he included specimens with dimerous and trimerous antennal clubs in one species, because he believed this was a sexual dimorphism. The female with the trimerous club is here excluded from the type series of S. alatus, and one of the dimerous males (with a historical label) is designated as the lectotype.
Franz (1982) ‘redescribed’ this species based on specimens collected by Besuchet, Löbl and Mussard. Examination of the aedeagus of the Nietner’s type specimens demonstrates that it is clearly different from that of specimens identified as S. alatus by Franz. The specimens examined by Franz and listed in his 1982 paper under the name S. alatus belong to an undescribed species.
The only Sri Lankan Scydmaenus whose aedeagus, illustrated in Franz (1982), is similar to that found in S. alatus, is S. alatus sensu Franz. As mentioned in the previous paragraph these aedeagi differ and the Franz’s species is not S. alatus. His illustration shows the aedeagus in dorsal and lateral views, and only the general shape (the median lobe tapering from base to apex) is somewhat similar, indicating that these two species may be related. This misidentified species was placed in Scydmaenus s. str. However, in the type species of Scydmaenus, there are two pairs of antebasal pronotal pits (see Jałoszyński (2016)), and both the true S. alatus and the species misidentified by Franz are devoid of pronotal pits. The subgeneric system of Scydmaenus is highly unclear and requires profound changes. Even though I have examined (by SEM) type species of most Scydmaenus subgenera, I was unable to place S. alatus in an existing subgenus. It belongs to the group of species with the metaventrite fully demarcated from metanepisterna by the anapleural sulci, a character that also occurs in Scydmaenus s. str. (some subgenera have the metanepisterna fused with the metaventrite). The two terminal antennomeres much broader than antennomere 9 can be found in the Australian subgenera Heteromicrus Franz, 1975 and Kingius Franz (in Newton & Franz (1998)), but they both have the metanepisterna fused with the metaventrite (illustrated for Kingius in Jałoszyński (2023)).
description: Published as part of Jałoszyński, Paweł, 2025, John Nietner collection of Sri Lankan Scydmaeninae (Coleoptera, Staphylinidae), pp. 79-109 in Zootaxa 5633 (1) on pages 90-91, DOI: 10.11646/zootaxa.5633.1.4, http://zenodo.org/record/15372835