Scydmaenus (Parallomicrus) myrmecobius Csiki
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Scydmaenus
Scydmaenus myrmecobius

description: Scydmaenus (Parallomicrus) myrmecobius Csiki
Scydmaenus (Allomicrus) myrmecobius Csiki, 1919: 73. New name for Heterognathus myrmecophilus Lea, 1912: 60.
Heterognathus myrmecophilus Lea, 1912: 60. Preoccupied, not Scydmaenus myrmecophilus Aubé, 1861: 197 (secondary homonymy in Scydmaenus); now not congeneric but replaced before 1961 and replacement name in use. (Figs 113–117, 198)
Type material studied. LECTOTYPE (here designated) (AUSTRALIA: TASMANIA): ♂ (Fig. 113), with labels illustrated in Fig. 198: “Tasm.H Vic.” [white, handwritten], “ Heterognathus / myrmecophilus / Lea” [white, handwritten], “ Scydmaenus / myrmecobius Lea ” / det. H.Franz ” [white, handwritten and printed], “Typus” [red, handwritten], “SAMA Database / No. 25-037031” [white, printed], “SAMA Digital Image / 21. Aug 2013 ” [green, printed and handwritten] (SAMA). Paralectotypes: TASMANIA: 2 exx. mounted on one card, with additional card with an ant Amblyopone australis Erichson, “myrmecophilus / Lea TYPE / Marrawah ” [white, handwritten], “15065 / Heterognathus / myrmecophilus / Lea / Tas: H vic.” [white, handwritten, with red “TYPE” along right margin], “SAMA- 25 43058” [white, printed] (SAMA); VICTORIA: 1 ex. mounted on one card with Amblyopone australis, “ Victoria ” [white, printed], “18396 / Heterognathus / myrmecophilus / Lea / Victoria ” [white, handwritten, with red “TYPE” along right margin], “SAMA- 25 43057” [white, printed] (SAMA).
Revised diagnosis. In male antennomeres 3–6 each strongly elongate, about twice as long as broad, antennomeres 9 and 10 each twice as long as broad, and antennomere 11 more than twice as long as broad, with rounded lateral margins (Fig. 112); metatibiae unmodified (Fig. 113); pronotum lacking antebasal pits; aedeagus in dorsal view (Figs 114, 116) with conspicuously narrow apex of median lobe, only as broad as 1/5 of widest (sub-basal) site of median lobe, flanked by strongly elongate, subtrapezoidal and weakly sclerotized lateral subapical lobes, each with small distal subtriangular projection directed dorsally, and with two small subapical groups of long setae, also directed dorsally.
Redescription. Body in male (Fig. 113) strongly convex, elongate and relatively slender, BL 1.88 mm; pigmentation uniformly light brown (including appendages); cuticle moderately glossy, covered with vestiture of setae slightly lighter than body.
Head (Figs 109–110) in dorsal view indistinctly transverse and somewhat subhexagonal, broadest at eyes, HL 0.30 mm, HW 0.33 mm; vertex and frons confluent and weakly convex, posterior margin of vertex evenly arcuate and anteriorly convex; tempora about 2.5 × as long as length of eye in dorsal view; supraantennal tubercles indistinct; frons over antennal fossae broadly subtriangular and with rounded anterior margin. Eyes small, weakly oval, not emarginate posteriorly and oblique in relation to long axis of head. Punctures on frons and vertex fine, inconspicuous; setae (including those on tempora) short, sparse, nearly recumbent. Genae (Fig. 110) 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. Submentum (Fig. 110) without submental lobes; hypostomal ridges (Fig. 110) extend mesally and anteriorly, but not connected at middle behind anterior margin of submentum. Antennae (Figs 112–113) long and slender, AnL 1.18 mm; three terminal antennomeres forming indistinctly delimited club; scape 2.5 × as long as broad, distinctly broadening distally; pedicel 1.8 × as long as broad; antennomeres 3–6 each strongly elongate, about twice as long as broad, 7 and 8 each distinctly asymmetrical and about as long as broad, 9 twice as long as broad and nearly cylindrical, 10 twice as long as broad and distinctly broadening distally, 11 much shorter than 9 and 10 combined, about 2.2 × as long as broad, indistinctly asymmetrical.
Pronotum in dorsal view (Fig. 109) distinctly elongate, broadest between middle and anterior third, PL 0.50 mm, PW 0.40 mm; anterior margin arcuate and laterally confluent with rounded lateral margins, so that anterior corners are not marked; posterior corners obtuse-angled and blunt; posterior margin nearly straight at middle and bent anteriorly at sides; base with very narrow and indistinct posterior marginal carina, lacking pits. Pronotal disc covered with fine and shallow, unremarkable sparse punctures; setae similar to those on head, moderately dense and long, suberect. Ventrally (Fig. 110) prothorax with nearly asetose and impunctate hypomera and basisternal region only slightly longer than procoxal rests, sparsely covered with moderately long recumbent setae, with short but distinct and slightly impressed anterior ‘collar’, and with distinct vestiges of notosternal sutures visible as notches on sides of anterior prothoracic margin; hypomeral ridges distinct and complete, demarcating narrow inner (adcoxal) region of each hypomeron, anteriorly running along procoxal rests and connecting at middle to form biarcuate anteprocoxal carina demarcating basisternal region posteriorly.
Elytra (Figs 109, 113) slightly rhomboidal, broadest near middle, EL 1.08 mm, EW 0.73 mm, EI 1.48. Humeral calli small but distinctly elevated and each mesally demarcated by shallow and transverse basal elytral impression; basal elytral foveae lacking; apices separately rounded. Elytral punctures fine and inconspicuous; setae similar to those on pronotum, moderately dense. Hind wings fully developed.
Mesoventrite (partly visible in Fig. 111) with carinate subrectangular mesoventral intermesocoxal process posteriorly fused with elongate and posteriorly broadening anterior metaventral process, fusion site distinctly marked on surface by transverse ridge. Metanepisterna (Fig. 111) fused with metaventrite. Metaventral intermetacoxal process (Fig. 111) broad and short, with strongly concave posterior margin, its lateral portions form short subtriangular processes weakly projecting posteriorly; distance between metacoxae subequal to 1/3 width of metaventrite at its posterior margin (excluding metanepisterna) and slightly wider than one metacoxa. Metaventrite (Fig. 111) weakly convex, unmodified and covered with sparse, short, slightly suberect setae, slightly denser on posteromedian area than those on sides.
Legs (Figs 110, 111, 113) long and slender; unmodified, except for slightly broadened proximal region of protarsi bearing tenent setae on tarsomeres 1–3. Protarsomere 1 nearly twice as long as broad, 2–4 each indistinctly elongate, 5 about 3 × as long as broad; mesotarsi longer than protarsi, mesotarsomere 1 about 3 × as long as broad, tarsomeres 2–4 each weakly elongate, tarsomere 5 about 2.5 × as long as broad; metatarsi slightly longer than mesotarsi, metatarsomere 1 nearly 3 × as long as broad, tarsomeres 2–4 each nearly twice as long as broad, tarsomere 5 about 2.5 × as long as broad.
Aedeagus (Figs 114–117) elongate but not very slender, AeL 0.50 mm, in dorsal view median lobe (excluding lateral subapical lobes) broadest near base, narrowing distally, then broadening in subapical region, to become strongly tapered in apical area, with apical margin weakly arcuate and as narrow as only 1/5 of median lobe at broadest site; lateral subapical lobes conspicuously large, each subtrapezoidal and strongly elongate, with additional subtriangular projection near apex, directed dorsally; flagellum broadened in proximal region to form three consecutive symmetrical chambers; median lobe with two small groups of long setae in subapical dorsal region directed dorsally; ostium situated in distal third of median lobe, far from its apex.
Female. Unknown.
Distribution. Known only from NW (Marrawah) and NC (Latrobe) Tasmania, and from CS Victoria (Lal Lal) (localities after Lea (2012)).
Remarks. Franz (1975) stated that the type material preserved at SAMA was composed of three specimens mounted on one pin, and farther in the text he refers to a holotype. However, the type series found in SAMA is composed of four syntypes, and a lectotype is designated here. Franz remounted one syntype (i.e., he removed one specimen from the original Lea’s card) and now it is on a separate pin, with handwritten copies of the original labels.
Scydmaenus myrmecobius has a relatively unremarkable external morphology; although its elytra are stouter than those in other similar species (mostly placed by Franz (1975) in Scydmaenus s. str.), it is easy to confuse this species with other congeners. Examination of the uniquely shaped aedeagus is the only unambiguous way to confirm identification.
Lea (1912) mentioned five studied specimens, “probably all males”; and he described “The middle trochanters each have a small acute tooth, projecting inwards and slightly forwards, but owing to its position it is not easily seen.” Such a tooth was not found in the studied syntypes, and I do not know of any species of world Scydmaenus with modified mesotrochanters. It is possible that Lea meant the distoventral corner of middle trochanters, which is subtriangular and can possibly be described as forming a tooth. However, this feature is common in most species of Scydmaenus and is not sexually dimorphic.
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 44-47, DOI: 10.11646/zootaxa.5371.1.1, http://zenodo.org/record/10144644