Scydmaenus (Scottiscydmaenus) optatus Sharp
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Scydmaenus
Scydmaenus optatus

description: Scydmaenus (Scottiscydmaenus) optatus Sharp
Scydmaenus optatus Sharp, 1874: 515.
Euconnus (s. str.) optatus (Sharp); Csiki, 1919: 50.
Scydmaenus (Scottiscydmaenus) optatus Sharp; Franz, 1975: 281.
Scydmaenus (Scottiscydmaenus) scotti Franz, 1975: 278. Preoccupied, not Scydmaenus scotti Lhoste, 1936: 611 (primary homonymy).
Scydmaenus (Scottiscydmaenus) scottides Newton, 2017: 16. New name for Scydmaenus scotti Franz, 1975: 278. Syn. n.
(Figs 135–144, 156, 160, 201–202)
Type material studied. Lectotype (here designated) (AUSTRALIA: WESTERN AUSTRALIA): ♂ (Fig. 135), with labels illustrated in Fig. 201: “ Scydmaenus / optatus / ♂ Type D.S.” [white, with black frame, handwritten], “Sharp Coll. / 1905-313.” [brownish, printed], “Type / H.T.” [white circle with red margin, printed] (BNHM). Paralectotype: ♀, “West / Australia ” [white oval, handwritten], “ Scydmaenus / optatus / ♀ Type D.S.” [white, with black frame, handwritten] (BNHM).
Additional material studied. Holotype of S. scotti Franz (AUSTRALIA: WESTERN AUSTRALIA): ♂ (Fig. 140), with labels illustrated in Fig. 202: “ Scydmaenus optatus Sharp / A.M.Lea det.” [brownish, handwritten and printed], “♂” [white, printed], “ Holo-type ” [white circle with red margin, printed], “W / Austra / -lia” {blueish circle, handwritten}, “Typus” [red, handwritten], “ Scydmaenus / (Scottiscydmaenus) / scotti m. / det. H.Franz ” [white, handwritten and printed] (BNHM); WESTERN AUSTRALIA: 1 ♀, Darlington, J. Clark (SAMA); 2 ♂♂, 2 ♀♀, Swan River, Lea (SAMA); 2 ♂♂, 2 ♀♀, Armadale, under stones, 09.06.1919, J. Clark (SAMA); 4 ♂♂, 4 ♀♀, Kelmscott, under stones with Ectatomma metallicum {currently Rythidoponera victoriae (André)}, 05.07.1919, J. Clark (SAMA); 1 ♂, 1 ♀, Swan River, each with Brachyponera lutea (Mayr), J. Clark (SAMA).
Specimens misidentified by H. Franz as S. optatus: 10 exx. from Sydney, Swan River and illegible locality in Western Australia, Scydmaenus spp., specimens lacking any profemoral modifications, smaller than S. optatus and with more erect setation, also larger females that cannot be identified (SAMA); 1 ex. of Scydmaenus mirus from Bridgetown with Brachyponera lutea, labeled as “optatus Shp? abraded” by Lea (SAMA).
Revised diagnosis (based on males). Head as long as broad (Fig. 156); profemoral tooth at most right-angled, broader than long or as long as broad (Fig. 160); length of temple in dorsal view about 3.5 × as long as eye; aedeagus in dorsal view (Fig. 136) distinctly broadened in subapical region, with truncate and indistinctly concave apical margin.
Redescription. Body in male (Figs 135, 140) flattened, elongate and slender, BL 1.75–2.29 mm; pigmentation uniformly light to dark brown (including appendages); cuticle moderately glossy, covered with vestiture of setae slightly lighter than body.
Head (Figs 135, 140, 156) in dorsal view as long as broad, rounded, broadest at eyes, HL 0.30–0.41 mm, HW 0.33–0.40 mm; vertex and frons confluent and weakly convex, posterior margin of vertex arcuate and weakly anteriorly concave; tempora about 3.5 × as long as length of eye in dorsal view; supraantennal tubercles indistinct; frons over antennal fossae broadly subtriangular and with blunt, broadly subtriangular anterior margin. Eyes small, almost circular, not emarginate posteriorly. Punctures on frons and vertex fine, inconspicuous; setae (including those on tempora) short, sparse, nearly recumbent. Genae as sparsely setose as frons and vertex. Anterior (exposed) region of head capsule demarcated from neck region by short abrupt impression around occipital constriction, anterior margin of gular plate on neck region with indistinct, narrow anteriorly-directed projection. Antennae (Figs 135, 140) long and slender, AnL 1.05–1.25 mm; three terminal antennomeres forming club, but antennomere 9 is so slender that club appears as dimerous; scape 3 × as long as broad, distinctly broadening distally; pedicel slightly more than twice as long as broad; antennomere 3 nearly 3 × as long as broad, 4 about 2.5 × as long as broad, 5 nearly 3 × as long as broad, 6 2.5 × as long as broad, 7 and 8 each about 1.5 × as long as broad, 9 slightly more than 2.5 × as long as broad, gradually but weakly broadening distally, 10 about 1.5 × as long as broad and distinctly broadening distally but again narrowing in short distal region, 11 much shorter than 9 and 10 combined, about 2.2 × as long as broad, nearly symmetrical.
Pronotum in dorsal view (Figs 135, 140) elongate, broadest near anterior third, PL 0.50–0.65 mm, PW 0.43– 0.53 mm; anterior margin nearly straight; anterior corners weakly marked, obtuse-angled and blunt; sides strongly rounded in anterior half; posterior corners barely marked; posterior margin weakly arcuate; posterior marginal carina obliterated. Pronotal disc covered with fine and shallow, unremarkable and sparse punctures; setae similar to those on head, moderately dense and long, suberect. Ventrally prothorax with nearly asetose and impunctate hypomera and basisternal region only slightly longer than procoxal rests, sparsely covered with moderately long recumbent setae.
Elytra (Figs 135, 140) evenly oval, broadest slightly in front of middle, EL 0.95–1.23 mm, EW 0.63–0.78 mm, EI 1.48–1.61. Humeral calli poorly marked, basal impressions and basal foveae lacking; apices separately rounded. Elytral punctures fine and inconspicuous; setae similar to those on pronotum, moderately dense. Hind wings completely reduced.
Legs (Figs 135, 140, 160) long and slender; profemur with short, broad and relatively blunt distal tooth (Fig. 160) slightly variable within studied specimens, but invariantly not elongate; protibia (Figs 135, 140) weakly broadened distally; protarsus with barely discernibly broadened proximal half and tarsomeres 1–3 covered ventrally with dense setae, of which only a few have spatulate adhesive tips. Protarsomere 1 1.5 × as long as broad, 2–4 each almost as long as broad, 5 about 3 × as long as broad; mesotarsi longer than protarsi, mesotarsomere 1 about 3.5 × as long as broad, tarsomeres 2–4 each about 1.5 × as long as broad, tarsomere 5 about 3 × as long as broad; metatarsi slightly longer than mesotarsi, metatarsomere 1 3 × as long as broad, tarsomeres 2–4 each nearly twice as long as broad, tarsomere 5 about 3 × as long as broad.
Aedeagus (Figs 136–139, 141–144) elongate and slender, AeL 0.48 mm, in dorsal view median lobe broadest near base, narrowing distally and then again broadening in subapical region toward truncate apex, apical margin indistinctly concave, with lateral groups of minute setae; flagellum broadened in proximal region to form three consecutive symmetrical chambers; ostium situated in distal third of median lobe, far from its apex.
Female. Externally differs from male in profemora lacking teeth. BL 1.85–2.05 mm; HL 0.35–0.40 mm, HW 0.35–0.38 mm, AnL 1.05–1.23 mm; PL 0.48–0.50 mm, PW 0.45–0.46 mm; EL 1.03–1.15 mm, EW 0.70–0.75 mm, EI 1.46–1.53.
Distribution. The type material comes from unspecified localities in Western Australia; all non-type specimens studied have been collected in SW Australia: SW Western Australia (Perth and vicinities).
Remarks. Franz described Scydmaenus scotti based on a specimen previously identified by Lea as S. optatus, but at the same time, he misidentified several specimens as S. optatus, including S. mirus Franz. Despite Franz’s (1975) diagnoses, descriptions and illustrations, the holotype of S. scotti (Fig. 140) does not differ from the male syntype of S. optatus (here designated as a lectotype; Fig. 135) in any important characters, except for being slightly larger and having a slightly more convex pronotum. The profemoral teeth and the aedeagi of these specimens appear to have the same shapes. As a relatively wide variation in size and proportions of body parts was found in all Australian species of Scydmaenus whenever a large number of specimens was available for study, this difference is treated as intraspecific. Consequently, Scydmaenus scottides Newton (= Scydmaenus scotti Franz) is treated here as a junior synonym of S. optatus (Sharp).
Scydmaenus optatus and S. swanensis are the only Australian species of Scottiscydmaenus with round, and not elongate heads (Figs 156 and 157 vs. 155 and 158). Even though both species show some variation in the body length and proportions of body parts, and the profemoral teeth in males do not show any differences (Figs 160 and 161), they can be easily distinguished by a clearly different body form, in S. optatus slenderer than in S. swanensis. The aedeagi of these two species are also clearly different; in dorsal view, the median lobe in S. optatus (Fig. 136) has a broader distal half than that in S. swanensis (Fig. 146).
description: Published as part of Jałoszyński, Paweł, 2023, Scydmaenus Latreille of Australia: Revision of species in subgenera Choleropsis Franz, Kingius Franz, Mascarensia Franz, Parallomicrus Franz, Scottiscydmaenus Franz, and description of Ascydmaenus subgen. n. (Coleoptera, Staphylinidae, Scydmaeninae), pp. 1-75 in Zootaxa 5371 (1) on pages 54-57, DOI: 10.11646/zootaxa.5371.1.1, http://zenodo.org/record/10144644