Microscydmus
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Microscydmus

description: Microscydmus (Scydmomicrus subgen. n.)
Type species: Microscydmus australiensis Franz, 1975, here designated.
Diagnosis. All characters as in Microscydmus s. str., except: tempora without thick bristles; bristles on sides of pronotum sparse and relatively thin or absent; setose impressions on mesoventrite absent, mesoventrite posterior to asetose impressions with only sparse setae; basal elytral foveae entirely asetose.
Description. Body (Figs. 20–26) extremely small, BL 0.50–0.65 mm; moderately convex, elongate and slender, with moderately long appendages; cuticle glossy; pigmentation in various shades of brown, usually uniform, in one species head slightly darker than pronotum and elytra; vestiture fine.
Head (Figs. 38–39, 42–44) with anterior part (in front of occipital constriction) about as long as broad, but vertex together with frons usually distinctly transverse; eyes moderately to very large; occipital constriction (Figs. 38–39; occ) only slightly narrower than vertex, groove marking the constriction running nearly continuously along dorsal, lateral and ventral surface of head; tempora (Figs. 38–39; tm) long and variously convergent caudad, without bristles; vertex (Figs. 38–39; vt) broader than long, convex, not projecting dorso-caudad; frons (Figs. 38– 39; fr) posteriorly confluent with vertex, transverse and subtrapezoidal with anterior margin variously projecting in middle, often forming distinct median sub-triangular projection extending anteriorly between large and narrowly separated antennal sockets (Figs. 43–44); frontoclypeal groove absent; supraantennal tubercles barely marked.
Labrum transverse with rounded anterior margin. Mandibles (Fig. 38; md) symmetrical, subtriangular, with robust and curved apical part, in the studied specimens sub-apical tooth and prostheca not visible. Each maxilla (Figs. 42–44) with subtriangular basistipes (Fig. 42; bst), elongate galea (Fig. 42; gal) and lacinia (Fig. 42; lac) and moderately long maxillary palp (Fig. 42; mxp) composed of short and slightly elongate palpomere I, strongly elongate, indistinctly pedunculate palpomere II, elongate palpomere III broadest near middle or slightly distally to middle, and narrow, strongly elongate palpomere IV with broad and short setose basal part and rapidly narrowed, strongly elongate and slender asetose apical part.
Labium (Figs. 42–44) with short and transverse submentum (Fig. 42; smn) fused laterally with postcardinal parts of hypostomae, without lateral sutures; subtrapezoidal mentum (Fig. 42; mn); and short prementum with distinct subtriangular ligula (Fig. 42; lg) that separates bases of moderately long labial palps (Fig. 42; lp). Hypostomal ridges (42. 10; hr) short and arcuate, directed postero-mesally, in one case relatively long (Fig. 44; hr), but not reaching anterior margin of gular plate.
Gular plate (Fig. 42; gp) large and subtrapezoidal with rounded sides; gular sutures (Fig. 42; gs) superficial; posterior tentorial pits (Fig. 42; ptp) small but distinct, located in transverse groove demarcating ventrally 'neck region' from anterior part of head.
Antennae (Figs. 42–44) short in relation to body, with distinct club composed of antennomeres IX–XI, antennomere XI narrower than X; antennomeres loosely assembled, with short but distinct basal stalks.
Pronotum (Figs. 20–26, 29–35) in dorsal view oval, broadest in anterior part, with arcuate anterior and lateral margins, posterior margin arcuate or slightly bisinuate; anterior angles not marked, posterior angles distinct but obtuse and blunt; sides without marginal carinae or edges; base or pronotum with four small pits, internal pair usually connected by variously distinct transverse groove or impression, external pits usually shallow or indistinct. Depending on species, transverse groove can be indistinct or even absent (Fig. 35, see also the Remarks section below) or internal pair of pits can be barely deeper than the groove and therefore indistinct. Sides of pronotum typically covered only with thin curved setae (Figs. 46, 48), in one case sparse and relatively thin bristles can also be seen (Fig. 47).
Prosternum (Figs. 46–48) with moderately long basisternal part (Fig. 46; bst) indistinctly demarcated from procoxal cavities (Fig. 46; pcc) by fine and somehow diffused carina; median part of sternum with weakly developed prosternal intercoxal process (Fig. 46; psp) visible as barely marked narrow longitudinal carina between procoxae; procoxal sockets (Fig. 46; pcs) closed by broad postero-lateral lobes of coxal part of prosternum; hypomera (Fig. 46; hy) elongate, divided into broad and setose lateral parts confluent with pronotal sides and narrow asetose internal (adcoxal) parts, adcoxal parts of hypomera anteriorly fused with prosternum, so that pronotosternal sutures (Figs. 46–47; nss) visible either as short notches on sides of sternum (Fig. 47) or externally not marked and visible only in transparent mounts, as structures concealed by anterior parts of hypomera (Fig. 46); hypomeral ridges (Fig. 46; hyr) complete, anteriorly overlapping pronotosternal sutures.
Mesonotum very small, mesoscutoscutellar suture absent so that mesoscutum and mesoscutellum form single subtriangular plate barely discernible between elytral bases in intact specimens.
Mesoventrite (Figs. 50–52) with narrow anterior ridge (Fig. 50; ar); mesoventral intercoxal process (Fig. 50; msvp) narrow and weakly expanded ventrally, anteriorly not fused or connected with anterior ridge, without posterior arms; asetose lateral impressions (Fig. 50; ai) present, area behind asetose impressions covered only with sparse and short setae; mesanepisternum with short prepectus (Fig. 50; pre) and posterior part largely hidden in ventral view; mesepimeron not visible in ventral view; sides of mesothorax without foveae; mesocoxal projections (Fig. 50; mcp) with mesocoxal sockets (Fig. 50; mscs) located on their mesoventral surface, without (Figs. 50, 52) or with small but distinctly protruding posterior lobes (Fig. 51: pl).
Metaventrite (Fig. 50; v3) elongate, anteriorly fused with mesoventrite, posteriorly moderately deeply bisinuate and with narrow median metaventral intercoxal process (Fig. 50; mtvp) composed of two long and sharply pointed spines. Metanepisterna and metepimera narrow.
Metafurca (Figs. 50–52) with very short and broad stalk and divergent lateral metafurcal arms (Fig. 50; lmfa).
Elytra (Figs. 20–26, 29–35) oval, each with single large and asetose basal fovea located in deep and large but short basal impression, foveae are circular or oval; humeral calli well-marked and developed as longitudinal protuberances; elytral apices unmodified, separately rounded.
Hind wings well-developed in all known species, about twice as long as elytra, with fringe of long setae along posterior margin.
Legs (Figs. 20–25, 46–48, 50–52) moderately long and slender; pro- and mesocoxae moderately elongate, metacoxae strongly transverse; all trochanters short; all femora weakly clavate; tibiae short and slightly thickening distally, without any noticeable modifications; tarsi short and stout. In one species (Fig. 47) males have procoxae bearing four small teeth in distal part of external margin.
Abdominal sternites (Figs. 50–52) unmodified, sternite III (i.e., the first visible sternite) with impressions expanding behind each coxae and demarcated posteriorly by distinct coxal lines (Fig. 50; cl), suture between VII and VIII well marked.
Aedeagus (Figs. 54–61) with symmetrical, lightly sclerotized and thin-walled median lobe, drop- or bottleshaped, with variously developed, symmetrical internal sclerites (in some species barely visible or with diffused margins), parameres present, not fused with median lobe, slender, each with one apical seta, in one species additional tiny sub-apical seta can be seen (Figs. 58–59).
Spermatheca (Fig. 50; sp) globular, moderately darkly sclerotized, located deeply in metathorax.
Distribution and composition. Microscydmus (Scydmomicrus) comprises seven species redescribed or described in this paper, distributed along the eastern coast of Australia, from the extreme northern part of the Cape York (N Queensland) to the Styx River (NE New South Wales) (Fig. 62 a–e). Additionally, two unidentified female specimens are housed at ANIC, collected in the Cape Conran (SE New South Wales) (Fig. 62 h). Apparently, species of this genus are broadly distributed along the entire eastern Australian coast wherever suitable habitats can be found.
Etymology. Scydmomicrus is an anagram of Microscydmus. Gender masculine.
Biology and collecting methods. Little is known about the biology of any species of Microscydmus (Scydmomicrus); available data refer only to the circumstances of collecting. According to label data, Australian species were collected from a variety of substrates in closed subtropical forests (rotten wood, leaf litter, "mixed litter", and rotten Banksia bark); one individual was found trapped by sticky seeds of Pisonia brunoniana (Nyctaginaceae). The most successful methods were Malaise traps and sifting appropriate substrates with subsequent extraction by Berlese funnels.
Remarks. Microscydmus tooloomensis sp. n. described below differs not only from the type species of Microscydmus s. str. but also from all Australian congeners placed in Scydmomicrus. Microscydmus tooloomensis has unusually long hypostomal ridges (Fig. 44); deep internal ante-basal pronotal foveae not connected by a transverse groove (Fig. 35), and the parameres with an additional short subapical seta (Figs. 58–59). All other features clearly place this species in Microscydmus, and it shares more characters with Scydmomicrus than with Microscydmus s. str.: the tempora (Fig. 44) and sides of pronotum (Fig. 48) covered with only thin curved setae and not with straight thick bristles; the sparsely and shortly setose mesoventrite posterior to asetose impressions (Fig. 52); and entirely asetose basal elytral foveae. The differences, however, require a closer study and a phylogenetic analysis must be carried out to clarify the taxonomy of Microscydmus.
description: Published as part of Jałoszyński, Paweł, 2014, The smallest Cyrtoscydmini of Australia: revision of Microscydmus Saulcy & Croissandeau and Penicillidmus gen. n. (Coleoptera, Staphylinidae, Scydmaeninae), pp. 1-30 in Zootaxa 3774 (1) on pages 11-18, DOI: 10.11646/zootaxa.3774.1.1, http://zenodo.org/record/285693