Microscydmus

Jałoszyński, Paweł, 2014, The smallest Cyrtoscydmini of Australia: revision of Microscydmus Saulcy & Croissandeau and Penicillidmus gen. n. (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 3774 (1), pp. 1-30 : 11-18

publication ID	https://doi.org/ 10.11646/zootaxa.3774.1.1
publication LSID	lsid:zoobank.org:pub:B5A2EF46-2BF6-4ED3-A5F4-5F9951400545
DOI	https://doi.org/10.5281/zenodo.5664966
persistent identifier	https://treatment.plazi.org/id/9A6687E6-4F19-303B-FF34-F94FFC55FDF6
treatment provided by	Plazi
scientific name	Microscydmus
status

Treatment

Microscydmus View in CoL (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 View FIGURES 20 – 28 ) 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 View FIGURES 38 – 41 , 42–44 View FIGURES 42 – 45 ) 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 View FIGURES 38 – 41 ; 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 View FIGURES 38 – 41 ; tm) long and variously convergent caudad, without bristles; vertex ( Figs. 38–39 View FIGURES 38 – 41 ; vt) broader than long, convex, not projecting dorso-caudad; frons ( Figs. 38– 39 View FIGURES 38 – 41 ; 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 View FIGURES 42 – 45 ); frontoclypeal groove absent; supraantennal tubercles barely marked.

Labrum transverse with rounded anterior margin. Mandibles ( Fig. 38 View FIGURES 38 – 41 ; 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 View FIGURES 42 – 45 ) with subtriangular basistipes ( Fig. 42 View FIGURES 42 – 45 ; bst), elongate galea ( Fig. 42 View FIGURES 42 – 45 ; gal) and lacinia ( Fig. 42 View FIGURES 42 – 45 ; lac) and moderately long maxillary palp ( Fig. 42 View FIGURES 42 – 45 ; 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 View FIGURES 42 – 45 ) with short and transverse submentum ( Fig. 42 View FIGURES 42 – 45 ; smn) fused laterally with postcardinal parts of hypostomae, without lateral sutures; subtrapezoidal mentum ( Fig. 42 View FIGURES 42 – 45 ; mn); and short prementum with distinct subtriangular ligula ( Fig. 42 View FIGURES 42 – 45 ; lg) that separates bases of moderately long labial palps ( Fig. 42 View FIGURES 42 – 45 ; lp). Hypostomal ridges (42. 10; hr) short and arcuate, directed postero-mesally, in one case relatively long ( Fig. 44 View FIGURES 42 – 45 ; hr), but not reaching anterior margin of gular plate.

Gular plate ( Fig. 42 View FIGURES 42 – 45 ; gp) large and subtrapezoidal with rounded sides; gular sutures ( Fig. 42 View FIGURES 42 – 45 ; gs) superficial; posterior tentorial pits ( Fig. 42 View FIGURES 42 – 45 ; ptp) small but distinct, located in transverse groove demarcating ventrally 'neck region' from anterior part of head.

Antennae ( Figs. 42–44 View FIGURES 42 – 45 ) 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 View FIGURES 20 – 28 , 29–35 View FIGURES 29 – 37 ) 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 View FIGURES 29 – 37 , 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 View FIGURES 46 – 49 ), in one case sparse and relatively thin bristles can also be seen ( Fig. 47 View FIGURES 46 – 49 ).

Prosternum ( Figs. 46–48 View FIGURES 46 – 49 ) with moderately long basisternal part ( Fig. 46 View FIGURES 46 – 49 ; bst) indistinctly demarcated from procoxal cavities ( Fig. 46 View FIGURES 46 – 49 ; pcc) by fine and somehow diffused carina; median part of sternum with weakly developed prosternal intercoxal process ( Fig. 46 View FIGURES 46 – 49 ; psp) visible as barely marked narrow longitudinal carina between procoxae; procoxal sockets ( Fig. 46 View FIGURES 46 – 49 ; pcs) closed by broad postero-lateral lobes of coxal part of prosternum; hypomera ( Fig. 46 View FIGURES 46 – 49 ; 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 View FIGURES 46 – 49 ; nss) visible either as short notches on sides of sternum ( Fig. 47 View FIGURES 46 – 49 ) or externally not marked and visible only in transparent mounts, as structures concealed by anterior parts of hypomera ( Fig. 46 View FIGURES 46 – 49 ); hypomeral ridges ( Fig. 46 View FIGURES 46 – 49 ; 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 View FIGURES 50 – 53 ) with narrow anterior ridge ( Fig. 50 View FIGURES 50 – 53 ; ar); mesoventral intercoxal process ( Fig. 50 View FIGURES 50 – 53 ; msvp) narrow and weakly expanded ventrally, anteriorly not fused or connected with anterior ridge, without posterior arms; asetose lateral impressions ( Fig. 50 View FIGURES 50 – 53 ; ai) present, area behind asetose impressions covered only with sparse and short setae; mesanepisternum with short prepectus ( Fig. 50 View FIGURES 50 – 53 ; pre) and posterior part largely hidden in ventral view; mesepimeron not visible in ventral view; sides of mesothorax without foveae; mesocoxal projections ( Fig. 50 View FIGURES 50 – 53 ; mcp) with mesocoxal sockets ( Fig. 50 View FIGURES 50 – 53 ; mscs) located on their mesoventral surface, without ( Figs. 50, 52 View FIGURES 50 – 53 ) or with small but distinctly protruding posterior lobes ( Fig. 51 View FIGURES 50 – 53 : pl).

Metaventrite ( Fig. 50 View FIGURES 50 – 53 ; v3) elongate, anteriorly fused with mesoventrite, posteriorly moderately deeply bisinuate and with narrow median metaventral intercoxal process ( Fig. 50 View FIGURES 50 – 53 ; mtvp) composed of two long and sharply pointed spines. Metanepisterna and metepimera narrow.

Metafurca ( Figs. 50–52 View FIGURES 50 – 53 ) with very short and broad stalk and divergent lateral metafurcal arms ( Fig. 50 View FIGURES 50 – 53 ; lmfa).

Elytra ( Figs. 20–26 View FIGURES 20 – 28 , 29–35 View FIGURES 29 – 37 ) 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 View FIGURES 20 – 28 , 46–48 View FIGURES 46 – 49 , 50–52 View FIGURES 50 – 53 ) 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 View FIGURES 46 – 49 ) males have procoxae bearing four small teeth in distal part of external margin.

Abdominal sternites ( Figs. 50–52 View FIGURES 50 – 53 ) unmodified, sternite III (i.e., the first visible sternite) with impressions expanding behind each coxae and demarcated posteriorly by distinct coxal lines ( Fig. 50 View FIGURES 50 – 53 ; cl), suture between VII and VIII well marked.

Aedeagus ( Figs. 54–61 View FIGURES 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 View FIGURES 54 – 61 ).

Spermatheca ( Fig. 50 View FIGURES 50 – 53 ; 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 View FIGURES 62 – 63 a–e). Additionally, two unidentified female specimens are housed at ANIC, collected in the Cape Conran (SE New South Wales) ( Fig. 62 View FIGURES 62 – 63 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 View FIGURES 42 – 45 ); deep internal ante-basal pronotal foveae not connected by a transverse groove ( Fig. 35 View FIGURES 29 – 37 ), and the parameres with an additional short subapical seta ( Figs. 58–59 View FIGURES 54 – 61 ). 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 View FIGURES 42 – 45 ) and sides of pronotum ( Fig. 48 View FIGURES 46 – 49 ) covered with only thin curved setae and not with straight thick bristles; the sparsely and shortly setose mesoventrite posterior to asetose impressions ( Fig. 52 View FIGURES 50 – 53 ); 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 .